Seriously, make friends with a painter. He can get it cheaper, but not by much. And why are you stuck on PPG? There are some other brands that work well and aren't sooooo expensive. I just did a job with a brand called Xtreme and it sprayed fine. Cost about 2/3 as much as the "popular" brands.
PPG is a great product. Keep in mind that spraying the paint is only part of its value. How long does the cheaper stuff hold its gloss, color and durability? OMNI is another great pruduct line, and it sells for a few bucks less than PPG stuff.
There is PPG and there is the "other" stuff. They are ahead of other manufacturers on the new water bourne stuff. They are also on 2 out of every 3 cars on the road in the USA today.