Looks like the Sawstop on Amazon costs between $1899 for a standard table saw and $3000 for a top line cabinet saw, with several variations in between.
The stop cartridge sells for $69.
The Bosch flesh detecting saw is $1499 for a "Jobsite" style table saw.
So about $1000 premium for the stop technology.
If they work - which by all accounts I've seen they do - Then any trip to the emergency room costs at least $1000 - whether you lose any fingers or not. It's probably a no brainer if you use your saw very often.
The challenge is for someone like me, who uses my table saw a couple days a year. My old Craftsman works fine and I choose to be very careful when using it - still it is a dangerous tool, and if I had an accident, I'm sure I would wish in hindsight I'd paid for a Sawstop.
I don't know how much margin is in that $1000 premium, and I don't know how much R&D investment he has to cover.
If there's a lot of margin in it then the guy could easily make the same money by lowering the cost and selling more units, and saving more folks in the process. Hard to say for sure whether it's just expensive technology or the guy is trying to gouge his customers.