I’m pretty sure that rental coffins are available.
In the case of a rental coffin (they tend to exist), you pay for the rental fee, and the liner. Someone else can speak toward liner fees, but I’d take a guess that the two fees together would still reach $750 minimum.
I remember when my German father-in-law passed on...the gal pulled out the catalog and I was surprised at the simplicity and cheap level you could go. You could have gone for a cardboard situation, and with no bells and whistles, maybe spent $500. After that, their five-star deal and best situation was around $20,000.