Yes, I have found that typically (not always) Toyota parts are cheaper than GM. When my Vibe was ready for its first oil change back in 2009, I went to the local GM dealer to get an OEM oil filter for it. The oil filter was $13.xx. It was a Toyota oil filter in an AC Delco box

. I ended up calling the nearest Toyota dealer (about 20 miles away) and asked them how much an oil filter for a 2009 Matrix XRS was. The parts guy told me $6.xx. Needless to say, ever since then I've been ordering the oil filters from Toyota. Like tpollauf said, I actually order them 10 at a time (since we have 2 Vibes) from TRD Sparks which works out to about $3.50 a filter. The only things I have ordered from GM are Vibe-specific parts i.e. interior parts and accessories. I always order GM parts through
GMPartsCenter.net as their prices are great, they offer free shipping (you only pay an $8.95 handling fee per order) and they offer discount codes (5% off orders over $50.00, 10% off orders over $100.00, etc.) pretty frequently. The only bad thing about GMPartsCenter is they do not ship to Canada.
I haven't been to the nearest Toyota dealer in quite some time, but the last time I was there, the parts manager was telling all the salesman, etc. that I had a Pontiac Vibe and I was ordering parts from the Toyota dealer. I told him, "Well, Toyota parts are cheaper. Of course I'm going to order them from Toyota!" Not to mention, the parts manager and other parts employees at the Toyota dealer are the nicest, most knowledgeable parts people I've ever dealt with. Don't even get me started on the morons at the GM dealer here in town

!