My most expensive fish currently is a Bartlett's Anthias, $55 at LFS. I don't tend to buy fish over around $80, as I can't stomach the loss when they occasionally die within days. My last $60 Potter's Angel lasted a whopping 2 days before dying in QT with no apparent illnesses.
I'd love to get a Helfrichi firefish, rhomboid and mystery wrasse, but they're so pricey. I'd also like an Imperator Angel, but they're too big for my 55 and I don't think my reef would enjoy it's presence anyway.
I don't want a gem tang or mutant clowns (snowflake) or that ugly hybrid tang on Live Aquaria).