$50.00 is reasonable for a captive hatched Staurotypus.
Does your salvinii have any hint of orange on it's head? I have seen a few that were really nice with orange flecks all over the head and neck. These were all captive raised adults.
There is a VERY COOL Japanese website that is all about Staurotypus and Claudius with a lot of really neat photos. Of course, the text is all in Japanese and you have to click on everything to hunt down the pictures but it's worth it.
BTW.......I used to feed my triporcatus frozen/thawed mice. It was messy and I didn't do it often but I felt the occasional mouse was OK for him.
You have to be careful that they don't get too fat on you---which they will if you let them.