Powerline adapters - Are they any good?

Are they as good as hardwired Ethernet, no not at all.
Are they significantly better then wifi, absolutely.
Real world speed of av500 powerline adapter (which is what you are likely looking at for that price range) is 70-100mbps.

As a comparison you would need a good router and good wifi chip to get more then 100mbps from a 300mbps connection in the same room as the router, once you loose line of sight the powerline adapter is the clear winner.