My 2 cents worth (I know, 4 cents Belize), the dives are NOT overpriced and I am all for the operators making a little more $$. It will allow them to maintain their boats and equipment, plus pay their staff a little better.
@ $75 US for 2 wonderful dives, you are picked up at your pier, ride for a few minutes and see incredible reef. I am not the "world" diver, but have dove in many places and 5 other countries, trust me it is a good deal. Multi-day dive deals are everywhere from what I heard and experienced.
Of course living in Texas, we are in love with Belize. It's close (no lay-overs or stops - Tropic Air doesn't count), it's clear water (the Gulf here is horrible), it's friendly, and the people are happy to have you there.
We paid $75 for a single, less than impressive dive in the Virgins (40', sand bottom, no marine life). Besides if it is too "affordable" everyone will show up and crowd the reef and have an adverse effect on the marine eco-system.
IMHO, of course.
Play, Love, Share and Enjoy - it doesn't last forever make sure you get the most out of it.