I've got this shirt in my collection too. Always thought it was worth a bit but never that much. Nice to know, even though I can't imagine selling it.
Also have the white Brains shirt from the 90s, and I've seen that on sale for over a hundred quid too. Would probably sell that though, not keen on it and looks more like a jacks shirt...
Imagine there's a small fortune, sitting in the bottom of cupboards of people on this board!