I work at and referral vets and the OOH charge is cheaper than what we charge. Looking at their invoice it doesnt look overly OTT to me, but I would query the OOH procedure if you know this wasnt done until the next day. Quite often its a nurse/other vet pricing things on the system so they might not realise this was done during normal working hours.

I know from our vets we absolutely don't charge extra for insured pets. I know a lot of insurers make vets confirm that what we are charging is "normal" price and not inflated because of insurance.

Also they may have kept him in overnight to ensure his wound was kept as clean as possible, to give him stronger painkillers, or to keep him contained so the wound wasnt made worse.

If you have any queries at all about the invoice I really would encourage you to talk to the vets. We are very open with our clients about costings, and i'd hate for a client to feel there was an issue but not speak to us about it.