It would be for the completed battery units with BMS. You would have to install the batteries into the battery cases. It is a bit tedious but it was otherwise straightforward. The batteries are extremely heavy.

I have always had good experiences with signature solar. My inverters are EG4 and I am very happy with their product after trying A LOT of others. I think the primary reasons for the price difference is that you are purchasing US inventory (it's already here), it's preassembled and warrantied as a unit, they provide pretty decent support and their battery packs use 100ah cells instead of 280ah+ cells. So you are buying ~3x as many BMSs, connecting cable ($$$$) and cases for the same power.

Their rackable units are not light but can be moved by a capable person without too much fuss. A fully loaded 280ah unit in it's case is over 250lb so you really need a lift cart or such. The 280ah units and now maybe 320ah are more economical.

There's some very significant additional costs of bus bars & holding racks, but holy heck man EVE LF280K batteries are amazing. Usually 300Ah cells/<$90. That's basically 1kWh of energy (~3.2V average ish).

Building a big 14s 14kWh serial pack is really not hard, albeit those small hardware costs (bus bars) can add up. Most people don't need that much energy, probably, but these cells are just epic, maybe go 24v if you want less. 8k cycle life makes them good for a much much much longer time than most cells.

Latest prices for highthium cells are $40/280ah

Do you know if these batteries be used as a replacement for batteries of a lead-acid UPS? I have a Tripp-Lite rack-mount UPS with an extension battery, but its battery has degraded and it can only sustain my computing load for 3-4 hours.

It'd be great to replace it with an LFP battery.

You can't use LFP batteries as a direct replacement in your UPS, no. The voltages and charge characteristics are different. What you can do is replace the UPS with a portable battery solution, like another poster suggested. I believe the Anker units are one of the few that can function as a UPS. Most sorta-can, but the key difference most of them lack is that they don't turn on automatically after fully discharging when the mains power comes back on. It's up to you if you need this particular feature.

Will Prowse on youtube I think has some videos comparing and contrasting the different units for this purpose.

Also, most of those power banks don’t switch between power sources fast enough to avoid causing problems.

That said, something I can confirm works on that front is getting one of those power banks, plugging the UPS in, and then plugging whatever into the UPS.

I had several days of uptime on Starlink that way, running it 10 hrs or so at a time on a battery bank, the remainder on a cheap generator.

I actually had a good experience replacing a lead-acid backup battery with an LFP battery in my garage door opener. I guess if the battery has an internal BMS and can accept charge at 52V, it might be enough?

The Anker units that are at minimum $600 per kWh? At that point we've completely lost the cheap factor.

I have seen Na-ion replacements for lead-acid, the chemistry is forgiving enough for that. No idea how good are they.

They can be used to replace ups.the voltages are close enough with lfp cells. I've done it. So long as you have a bms, there is nothing to worry about

For that low a power need Anker and some others make ready to go units you can buy off of amazon that are pretty reasonable.