We're mostly on the same page, but there are some caveats to buying the heavier bulbs, even assuming the weight is all heat sink- because that won't matter if the heated air has no where to go!
An expensive bulb with a nice heat sink will fail just as quickly as a cheap one when you put it in a well-sealed can light or something else that traps all the hot air.
If one bothers to care about heat sinking, they might actually test the thing and opted not overdrive it. It's just a good totally layman indicator.
Funny enough most mains/350V DC, chips tend to have a limiting resistor for the current drive - lower resistance = high current. Most (if not all) have two resistors in parallel (for a better control, and less power per resistor) - desoldering one would greatly improve the lifespan for a minimal luminosity loss. So by picking a larger heatsink, they might picked a bit large value for the resistors as well.
An expensive bulb with a nice heat sink will fail just as quickly as a cheap one when you put it in a well-sealed can light or something else that traps all the hot air.