Is there any data that backs up that GM buys their parts from Toyota??
I think GM buys their parts from the suppliers, just like Toyota does.. so Yazaki, Denso Michigan, the fascia manufacturers, etc etc... GM doesn't buy the headlamp from Toyota.. it's unique to the Vibe, same with almost every exterior stamping (black metal is probably identical - door inners included, B-pillar etc..)
I find my Canadian dealer to be on par with Toyota for many of the items, yes, Toyota as a general rule is much cheaper than any OEM for parts over the counter.. indeed..
But, I thought the cabin air filter box was the same, (thinking the same filter even).. well, it's not.. so, there are indeed differences.. (why did they bother engineering another cabin air filter/box ?!?! setting up a tool for it, different part number, etc etc..., it costs a LOT of money to do something minutely different.. that's why the Chevy Aveo5, Pontiac Wave5, and Suziki Swift are all totally identical, less the instruction manual, badges and grille insert!!!
Anyhow, I'd like to know more about GM buying their parts from Toyota, could be?!? dunno, but the alliance works for both parties.