Bag. This cost $3.99 at Toys'R'Us, which gives us a Price per Piece of $0.10.
Instructions & Minifig.
Parts. In general, I don't like wheels. I have built a few wheeled vehicles before but I don't go looking for them. Hinge parts are always good. I like the 1x2 Plate w/Bar (open ends) and the 1x2x1x2 bracket. I'm not so sure about that lift bucket though.
Self-Propelled Gun. It's not a bad looking little vehicle. I'd
stat it out as 3Ra/1Rd (gun) / 1B (hull) / 1G (wheels) /2W.
Can you build a frame, or frames, right away? Yes. (+5)
Is it below, at, or above the golden ratio? At. (0) (The Golden Ratio is $0.10 per part.)
If you can't build a frame right away, or choose not to, does it have parts you should be able to put into use right away? Yes. (+5)
Does it have more than a handful of immediately useful parts? No. (-5)
Score: B+ (+5). I really like the Self-Propelled Gun design I came up with. It's not too far off the base design of the set and a bunch of these could make for a fun squad. The only problem is you're going to be stuck with a minifig afterwards.