Yes, Plextor as well as Pioneer don't make their own optical drives anymore. Pioneer is divesting itself of a lot of products (TVs, home audio and video, computer peripherals, etc) and as a company is actually shrinking.
I have a Pioneer DVR-217 D, and it rocks. It's also relatively quiet as optical drives go. I don't know why the OP thinks they are more expensive, I paid around the same as a similarly spec'd Samsung for my Pioneer.
I've also heard good things about Sony Optiarcs (which used to be the NEC optical drives).