Idk it depends on the bra. The cross dressing guy I sold to liked new, nice clothes and shoes, so I priced high, and he understood that. I would see if other people are offering anything similar, and what they are pricing it at. However, of course remember there's gonna be the expense of mailing involved too, as well as the hassle of going to a post office, which you should be compensated fairly for. Sorry if I sound bossy, I just wanna remind you of those, because I used to always forget about those parts myself.
Oh and also...it may be worth limiting to US only. I have had issues with higher mailing expense than anticipated as well as customs, with both Norway and Canada. If you do offer international, be sure to add on an extra charge for that, so you don't lose money on mailing expenses. Ok, sorry to sound like a mother hen lol.