Back in 2021-10-06 when I bought mines, they were crazy expensive!

I paid 89239 SEK (~9349 USD) +25% VAT = 111549 SEK (~11685 USD) per unit.

Not sure about the VAT rate if buying from US.

Hopefully they have reduced the prices since then, not sure.

how long do these last? you seem to have made a huge capital investment here

Not sure, haven't even tried them yet, still renovating the house, three years and counting. But according to the specs:

    L70 ≥50,000 hours at 25°C ambient

L70 is "An LED is considered to have reached its rated life at that point in time when it emits 30% less light than it initially did. This 70% brightness level is termed “L70” and may also be referred to as Lumen Maintenance." (https://nunvdata.unvlt.com/uploads/Understanding_L70_and_Why...)