3D printer services?

[ffutures]

I need a really small lens cap (the rear cap for Pentax's old 110 film cartridge SLR's lenses), and the only person who has them  for sale in the UK is printing them and charging £5.49 each (£4.04 each for 4 or more) for something about the size of a couple of 10p coins stacked togeher. You can download a template with a Creative Commons license free. So I'm wondering if it's worth looking for a service in the UK where I can order one printed (or maybe a couple in case I get another lens) that won't cost an arm and a leg. I have no idea how you cost these things, if anyone can take a look and tell me it's this one:

https://www.thingiverse.com/thing:4526905

Is £5.49 / £4.04 in bulk actually reasonable? I really have no idea.

Later - a friend who has a 3D printer has offered to run off a few for me - one to use plus spares for any lenses I acquire later. His estimate of costs is 37p per cap...