If they are cheap then surely it makes it even less likely they would patch out the DRM, as the gain in sales revenue would be reduced compared to a full-price title and they'd still have to pay the cost of removing the protection, QA etc.
Personally I just bought the game in the sales a while back, played through it, job done, never even noticed any DRM. Obviously if you're planning on formatting your PC in the near future it could be an issue but I don't know why people get so worried about it.