This happens to me regularly. I'm generally searching for 2 adults and 1 child, which I know exacerbates the issue, but still annoying that the results display is less than genuine. My favorite recent example:

5 night Award Stay in Singapore
The Vagabond shows available for 150,000 points for the stay
Click "Select Room" and price jumps to 600,000 points because I can only book a suite for 2 adults and 1 child

Searching for awards for an upcoming stay in London often shows several properties in the 230,000 to 260,000 point range for 5 nights only to find that there is a cash component anywhere from ~300 to 1,500 GBP on top.

I've grown more accustomed to it and have tried to take the approach of, "let's see if that's really the price," but every once in a while I see what looks like a deal, get excited, and then not so much.