When was the last time you had it done for less?
Not too many weeks back. Was so trivial it wasn't worth charging extra for. Run some power, add a regulator and a few other bits, extending the length of the board slightly (ok, the actual circuit itself was a cut'n'paste from a previous job with a little bit of changing to make the final design aesthetically pleasing to me). Litterally ring ring "Hello?" "Hi, so-and-so here, just wondering if you could add a 5v output to the unit?" "Would a USB socket do?" "Yes, that'd be great! How much extra?" "For you, no charge.".
In a case like this I'd've suggested exactly that, chuck a buck charger on there (never really sure if they call them "buck" because of function or cost!) and be done with it.
I've also built a number of projects where I've tossed in a cheap USB charger socket for voltage regulation. They're so cheap and readily available. And the circuitry is so simple, hence why I also cannot see the $800 as anything less than theft.
The guy deserves all he gets for ripping off his clients, and clearly does not have a shred of integrity.