I'd be interested, but like Michael said the concern is print time. As far as price goes, I think you need to do a backwards evaluation; start from what you will retail these at, subtract the profit you want, and see how much you have to pay for everything else. My guess is that this will leave little to subcontract printing (don't forget that you'd have to cover shipping on top of payment) or you'll have to charge a premium and never sell any. Either way, unless you find people that are passionate about your product, we'll want to get paid regardless of whether or not you sell them.
If you do decide that theres still profit in it, heres how I could see it working (for me at least):
1) You pay for a roll of filament that would be used only on your project. This keeps the printer from having to absorb the cost of failed prints and as a result you would get cheaper pricing (since we'd take less risk).
2) You pay for shipping including shipping materials if needed
3) Paying 1 and 2 means that the printer would just charge for run-time on the machine.
The primary downside to this system is that you would have to trust the printer. Otherwise you'd just have to pay for each enclosure just the same as if you were buying a product, but that means that it'll be more expensive for you since we'd have to absorb all of the risk.