yeah mine take a washer. Did you scan yours or design from scratch? I had to make tweeks to the standard design to optimize for FDM printing so designed from scratch. Took Quite a bit of working out.
Cost with washer in PETG is about 45-50p each instead of £2 each so about 1/4 the cost. if your using allot of em it adds up quick, just these alone basically paid for the printer.
I have some more optimizing to do to tighten tolerances and need to try printing in ABS as PETG is not quite rigid enough to be ideal and PLA dosent have enough layer bond strength to print upright.
I'm waiting for my PRUSA Mk3 to arrive before I experiment with things much more and just printing what I need as I go at the moment (ie batches of 10). You need a good FDM printer for this that prints reliable otherwise its more hassle than its worth.
With dlp/lCD resin printing a plate of these would be tons faster, but from what I can tell resins are not as robust as fdm materials like abs/petg (could be wrong just going on comments from forums rather than own actually experience at the minute)
Took allot of time and working out to do this but learnt loads about 3d printing process/design and materials during the process.