As far as I'm aware PCOS (polycystic ovarian syndrome) and polycystic ovaries are the same thing.

I assume it does cost more to transfer at blast stage, but we only have one provider where I live so I haven't shopped around. I don't really know why some clinics do Day 2 transfers given that the more advanced embryos become apparent at Day 5 stage. I've never figured that out. That said, heaps of people get pregnant from Day 2 transfers. There is a thread on this topic under the LTTTC/AC section thread summary.