So just checked out the options that deathjester suggested.
In 1/72, the only C-17 option I can find is from Anigrand anyways, and at $185 to boot, so for that scale, may as well just go for the Anigrand YC-14.
In 1/144, which I'd prefer for such a large aircraft, going by Squadron's prices, it'd be $30 for a Minicraft C-130, $28 for an Amodel An-72 and $36 for a Revell C-17... so total $94 before shipping. Add all the putty etc., and then you're left with a huge pile of leftover plastic...
Too bad Anigrand doesn't do this in 1/144. At the $100 average their kits in that scale seem to go for, I could probably (at a stretch) justify one to myself. At $150 for one in 1/72... well, that's a reasonable price, all things considered, but I have no idea where I'd put it...