I got a little lucky that I already had some scrap wood (mostly the plywood and Masonite), I just had to buy 2x4s. But it was definitely under $100. And honestly, I think I over built it a bit, I could've gone with a single peice in places I used 2, and could've used 2x2s in some places too, to save money. But still not that expensive. The laminate sheet was the most expensive single thing.
Ya they really were. When I got them they weren't the same finish, so they stood out as being different, but I had already planned on painting them so I wasn't concerned. So keep that in mind if you have to get cabinets from multiple people (which I did) that their current color /finish isn't important, just paint them!
Well, when doing the storage shelves on one side of the garage, and the long work bench on the other... Garage floors AREN'T level, they're higher at the back and lower at the front (for drainage in case the water heater bursts)... So keep this in mind during planning, and make several measurements along the wall.