Sights got expensive when people started paying more for them.  The market wanted slider sights and they built them better.  Some of the cheaper built sliders should be $125-150 max.  Those $400 black gold sights are a real disappointment.  They should be in the lower price range.  A nice quality sight should go for $200-300 at the upper end.  The UV sights have no justification for their price, other than somebody out there is paying for it.  It's hard to beat the value of a fast eddie 2 pin.  CBE and axcel used to have a pretty good value too but they've gone up and the quality has gone down.
So, in short, stop paying too much for your sights and the market will correct.