When I was still diving SP regs for my dive program, I had a good relationship with a dive shop and I did all the service there myself, and had ordered a bunch of parts kits. The shop went out of business, so I then had to take a fleet a regs to another shop to have them serviced (no corner cutting for an institutional dive program, so even though I was trained, I was no longer authorized to service). I had the parts kits anyway, so I took those as well.
They charged me a $25 fee for each parts kit of mine they used, so $75 per reg. I was not happy with that surprise bill for 15 reg sets. Especially when I had to go back and re-tune a third of them and rearrange all of the hoses, since the new shop set them up with a swivels up.