Before I get really wordy, TL;DR:
1) the creator M_BERGMAN on Thingiverse.com has some really great WW1 and WW2 tanks.
2) don't be put off by 3D printing layer lines, they are far more visible in photographs
3) Monoprice Mini Delta at $159 USD is an easy to use printer
Lots of people are posting for free or for sale STL files of all kinds of things that would make useful minis. They are usually shown as renders, rather than photographs of prints. This is a problem, because not everything prints well. Some things look great as renders, but are smudgy blobs when you print them. Some files may work in video games, or they may be perfectly accurate 3D scans of the original object, but neither of those means they will look good as prints. I am and I encourage others to be extremely skeptical of STL files intended for printing shown only as renders.
And as I think we know a perfectly scaled representation may make a terrible miniature. Sometimes features need to be exaggerated to be visible at all.
In any case, the M_BERGMAN person is a gentleman and a scholar, as skilled as he is generous. I think he posted something about "something to draw at lunchtime" but he has uploaded to Thingiverse.com several "packs" each containing dozens of AFVs, along with a few trucks, etc. There's one for WW1 and four or five for WW2. They are scaled at 1:200, and they look really, really good printed as is. That is conveniently (?!) in between 15mm aka 1/100 and 1/285 aka 1/300 aka 6mm. I have not tried scaling them up and down, but I'm optimistic based on the quality at 1:200.
These files are free, if somewhat quirkily organized. FREE!
link
I've also discovered that while the layer lines are highly visible in photographs, they are not at all prominent in real life, even with my glasses on. In your hand, on the table, they are fine. Take a photo and it's hideous, paint or no paint. I'm sure some people are going to be more sensitive to this than others. These models off my cheap 3D printer are perfectly satisfactory to me, though I suspect some people would not accept them. They are not as good as the highest quality cast pewter pieces, mostly because of the lines.
So whether or not you can have all the Shermans you want at a nickel apiece depends entirely on how you feel about the lines, but don't decide based on photographs, the lines are less prominent in person.
I did some *extremely* slap dash paint jobs on them, literally standing up in the kitchen, just to see how they would look painted. They take paint pretty well. The stripes on that Tiger II are awful, and the paint does not reduce the prominence of the layer lines much, but otherwise it works very nicely. I'm afraid to use a wash because I think it will highlight the layer lines more than anything, but a dry brush will probably work.
These had minimal clean up. With more time they might look a little better. Also, some of the barrels were printed without support, so where you see drooping lines underneath barrels that's something that can be fixed in the slicer settings.
Also, cats like to chew on PLA. It's non-toxic, but you may still want to keep your tanks away from the cats.
Finally, I spent an hour getting my Monoprice Mini Delta up and running again and have been running it nonstop for days. I'm still getting some warping with long items (over 50-60mm), but for small things it's great. Printing these tanks, with their turrets beside them, takes 20-35 minutes.
BTW in the pictures where you see two Shermans side by side that is a comparison of the default and "Fine" resolution print modes. There is not much difference. The ones on the left with the red dots on the starboard rear are the "fine" ones.
I also have an issue with dimensional accuracy – meaning if I print something 80mm long it comes out as 78.5 or 79mm long. This is an issue if you're printing something that will interface with the real world, like a replacement part for something or a utility blade holder, but it doesn't matter much for other things. When necessary I scale things up to 102% or 102.5% and that is close enough to make useful things for the house and car.
The other limitation of this printer is its small print area – basically a cylinder about 4" in diameter and 4" high. But a printer I would trust to be easy, reliable, and accurate with a larger print area would be $400 USD-500. Hopefully I'll get one someday, but for now I am having a blast.
So if you're looking for a cheap and easy 3D printer with a decent feature set I recommend the MP Mini Delta.
Now I want to go buy some olive drab filament…