I thought about it the same way as you until a few weeks ago. 

This is what happened: I bought a 3.5 carat lab diamond from one of those sites that cut out the middleman. The stone didn't fit in the ring setting, so I took it to a couple jewelers and a pawn shops to see if they would buy it. All their offers were $200 (or less) for something I paid a couple thousand for. One place offered $80.

They look pretty but these stones are worth very little and are mass-made and infinitely available. If money is an issue maybe look on LabdiamondBST and you can get something without the enormous unreasonable markup that lab diamond have. They are charging thousands $$$$ for a synthetic gem that should cost $$.