The prices on those bikes are ridiculous. If you buy something like that please buy it second-hand from someone that had more money than brains and thought they were going to lose weight by buying a bike rather than using it. Usually these go for a fraction of their new value in mint condition once the new-years vows have worn off.
I picked up my first "real" (not a department store bike) mountain bike, a giant NRS XTC, in 2000. That bike cost me $1800 which I thought was outrageous. But, it was basically a top of the line giant at the time, complete with nearly the best components money could buy.
I rode it weekly for a decade on trails designed to destroy bikes. I replaced it with a lower mid-range trek superfly fs a couple years ago. That bike cost me nearly $4k. And besides the 29" upgrade (which makes it weigh more) I'm not convinced its actually a better bike. For sure, the more expensive versions (which were pushing $10k for the carbon versions) weren't a better ride.
So, I agree the prices for mountain bikes are ridiculous, especially if you don't buy into the idea that there has been a lot of technology progression since the late '90s early 20s. Most of the "progression" seems to be more style than substance. Take the recent axle/skewer fiasco. The general claim was that the skewer was a problem so it needed upgrading, but who has actually had a problem with them? Absolutely no one I know, has ever had a wheel come out of a front fork unless they failed to tighten it. Nor do I buy the idea that its more stable because the skewer wasn't providing any rigidity to the front fork, that was the job of the axle (which if you notice is the part that makes contact with the fork for all directional forces except laterally). In the lateral case fork manufactures were putting locking indentations in forks since the early 90's. Further unnecessarily changes, 27.5" wheels, nonstandard head tubes, etc.
The lack of _ANY_ competition in "local bike shop" sales channels due to franchise licenses and regional restrictions also serve to easily quadruple the prices too.
Bottom line is that I agree. Buy a used bike if you can. I'm pretty particular about size/fit so its harder for me, but people who are closer to average size don't really have an excuse.
A mid-range fork today is so much better than a mid-range pogo-stick fork from the 90s.
Better forks & shocks as well as a slacker headtube-angle on most bikes today make todays bike a lot better to handle and ride, and inspire a lot more confidence than a bike from the 90s.
I do agree prices are high, but you do not have to have a $10k carbon bike to have fun or win races.
Also, narrow/wide chain rings, clutch derailleurs and a far greater range of available gearing options has advanced the entire drivetrain compared to 5, 10 years ago...and lets not forget all the advances in disc brake technology over the years.
You are right, but it makes a bigger difference than you suspect. My bike has a 2x10 setup right now, and I am most likely converting that to 1x10 or paying up for a 1x11 setup in the future.
Not having to choose between 1-2 on the front and then the back gears simplifies things greatly. In addition you also save some weight, it's a much simpler mechanic with less maintenance and with a newer SRAM Type2 or Shimano Shadow+ Clutch derailleur and a narrow-wide front ring you pretty much can't drop a chain, which is great. The only exception would be if you ride incredibly rough terrain where you bounce a lot, but a very simple chainguide fixes that problem.
Those aren't the sort of bikes that people buy in order to lose weight. They are more like mini MotoX bikes without the engines. They cost a lot because they are built to be extremely strong and have brakes which work well at high speeds in bad conditions which is important when you smash it into a tree at 40mph.
The risk with buying a bike like that second hand is that it may have already been crashed/damage.
I have some insight in the 'new bike sale' process for brand bikes. The margins are very healthy. I buy 'regular' bikes brand new and I won't argue about the price, the margin on those is a lot lower.
The margin on high end (road/mountain) bikes is insane and their performance is not substantially different from last years issue (which can be already had at a subtantial discount new), second hand ones are much more realistically priced.
If you feel like overspending and/or justifying that then be my guest but there is no rational reason why last years model should be worth half of what this years model is worth.
That's why there are 'model years' in the first place, they are simply a device for getting you to upgrade, this suggests that there is a lively second hand market where you can find something of almost the same functional value for a small fraction of the new sticker price.
In that second hand market you will find bikes that have been used heavily in that first year and bikes that are 'good as new' and the prices won't be too far apart, usually around 40-50% of what a new one costs.
For instance, this bike is $6600 new but discounted to $2495
You'd need to inspect it and make sure that it is really 'only a scratch' rather than that it has impact damage but that's doable if you know what you're buying. And if you don't then you do not have a good reason to spend more than $1000 on a mountainbike anyway. (The difference between a $1000 second hand bike and a new one that's 5 times as expensive are still not large enough to justify the difference in price).
Craigslist is another good source for hardly used bikes at a fraction of their new price.
As for impacting stuff at 40Mph, your carbon bike will be bits and pieces at those speeds, an aluminum bike will be still in one piece but ready for the shredder.
If your main concern is impact damage to your bike then you have been very lucky so far. In my opinion the main risk in mountainbiking down-hill with trees next to the track is impact damage to the rider, not the bike.
Just be aware that second hand bike generally have no warranty on the frame. That may or may not be a concern. If you know what you are after getting a bike second hand and getting the parts off it can be a great way to get exactly what you want.
I'd also point out that you can get really good deals on bike when the model year changes over.
(I only do road bikes, but I'm sure it's pretty similar for MTBs).
Mountain bikes are never in a new condition for long if ridden regularly. You are going to crash it sooner or later and you need to check for damage regularly. A lot of the parts will need overhauling or replacing within 6 months. A well maintained 2 year old bike can be in better condition than a badly maintained 6 moth old one.
There is hardly a bike frame on the market that can survive actually hitting a tree at even 10mph with the rider on it.
Most of the frames are extremely strong vertically, but if impacted on the side or directly on the tubes crumple like the couple mm thick aluminum/carbon they are.
At the world cup finals in Hafjell, Norway last weekend, the top guys were hitting 82 kmh (51 mph~) on a open section speed trap. They aren't quite as fast in tighter sections, but still plenty fast.
Here is the helmet cam footage of Josh Bryceland that probably would have ended up winning if he had not overshot the last jump and broken his foot. https://www.youtube.com/watch?v=XBDpu4-pQhM The speedtrap is at about 2:30.
