I recently bought 250 superworms at mealwormsbythepound.com (I think they were in the vicinity of $18 including shipping) and am really happy with them. Not a single one was dead, or has died since, and I'm pretty sure I got more than 250. They're big and fat and I will definitely be ordering from them again.
A footnote - every now and then there must be an escapee, because we find the occasional big black beetle. I try to keep a damp cotton ball in our guest
bath cabinet, because that's where we always find the beetles - when they finish their metamorphosis they must be
thirsty. Whenever we find one of these dudes we immediately give it to Richard. The ONLY time he moves fast is when he sees one of these beetles - they're his absolute favorite thing!