Bit of an odd one here, but if, like me, you frequent toy stores, you may have seen "Nano Metalfigs", a range of roughly 1/48 diecast figurines.
http://metalsdiecast.com/nanopacksize/singlepack/ Now, the sculpting on their range of Marvel, DC , Harry Potter, Disney, Halo, Pro Wrestling and Street Fighter varies and never really comes close to "real" miniatures, but it is the cheapest 28mm(ish) Hulkbuster I've found. If you're super keen on adding Harry Potter and the Undertaker to your collection, that's your damage, but Baymax and Mr Incredible are nice enough and in the right scale.
It's also worth noting the really nice Batcave that I constantly struggle to not buy:
An odd one, but worth mentioning.