The cost for me is hard to estimate. My wife bought me the printer (a wanhao duplicator i3 clone) for my birthday so I suppose that can't really be factored in, but at some point it might be a consideration. The 1kg spool of PLA material it's using to "print" the enclosures was $23. ABS and PETG prices are similar.
A single mcModule enclosure with lid from the files linked above on "fast" takes this printer 45 minutes and it says it requires 6 grams of material, but I decided to put 3 of them down at once, which for some reason took 2 hours and 19 grams. I had no trouble with those...
... but I'm trying to print the gateway and lid now, a much larger set of objects, and it says it will take 5.5 hours with 39 grams of material, but I've failed 3 times now and aborted after about 3 hours each time, so that's material wasted. I probably need to clean the bed better, or maybe try just printing the lid and base separately.