50 for the vamp souds great to me. A LFS around me had a small one (under 4") for 40. the gar seems High at 150 but I swear I saw someone selling them for like 25 bucks at like 8" I could be wrong though. But I am sure yours is in much better shape.
I can't really help you with the vampire tetra because I've never seen them for sale around me
But to give you an estimate on the gator gar a month ago at a fish shop in RI I bought an 8"gator gar for $25 in excellent shape, original price was $50 but because I was buying a lot of other fish I got it for half price.