Well,
most expensive fish: $75 Sailfin Tang and $75 Blonde Naso
most expensive coral: $295 for a large SPS colony (SHHH, my husband things it was only $95) $80 for a single head of golden torch
$80 for one rainbow acan head, couple SPS are in the $80 range too
most expensive purchase at one time: $150lbs of LR at $10/lb
We are lucky, we have some really expensive pieces and fish, but the LFS that is closest to us has amazing prices. We also know a lot of people in the hobby, so I have pieces that are worth more than double what I actually paid.
I would easily pay more money for the right piece.