If you buy MTM boxes in bulk at Midway they can be had for around $2 a box. That's what I did with several sizes some years ago, when they were even chaper, and still generally have some of the right size on hand for a new project.
These threads always kind of remind me of one where a guy mentioned how much he'd paid for his brand-new pre-'64 Model 70 Winchester in 1950-something. Whereupon several other guys (not just one) said they would buy a LOT of pre-'64s at that price. Of course, the guy that bought the rifle was making less than $400 a month back then...