Let's suppose, hypothetically, I were to design a range of 3D printed miniatures for a game - let's go with spacecraft, since vehicles are actually more feasible on current hobby printers than figures, and spacecraft mean you can even get away without wheels.
To get it pre-printed by someone like Shapeways, you'd be looking at about $25 for a large ship (15 cm3 print volume) and $10 or so for a smaller one (7 cm3). Let's then suppose that a typical fleet is half a dozen large ships and, say, ten small, from a total of three designs each of the large and the small.
FX: counts on fingers...
That's $250 or so. Call it UKP 160 or so (yes, I know the dollar exchange rate is a bit variable at present, but lets work with the figure of 160 quid's worth of 3D printed starships for a single fleet). That seems to be a reasonably comparable price to a similar fleet in other materials (feel free to correct me if I'm wrong).
Supposing you own a 3D printer of your own...
What's the right price for those six designs?
Assuming the 'pre-printed' ships are done in Shapeways "white strong and flexible", I'd be paying Shapeways $1.40 per cm3, which works out around $170-200, so you'd be paying me (for the sake of argument) $50 for the intellectual property, the design work, call it what you will.
So: would you pay $50 for the 3D files for those 6 ships? Say $12 for the large ones, $6 for the small, and a package discount for the lot? Fundamentally, I'm basing the figure on the typical amount of money I'd make from Shapeways if you ordered a representative fleet. Assuming you already own a printer, it's going to cost you (relatively) peanuts in ABS or PLA off-the-reel (not at Shapeways prices!) and power.
What if I said (purely on an honour basis): "those designs are for your personal use. If you want to print stuff for your club, or your mates, the price is $100 for the bundle"?