My advice is to shop around for a CAMO that isn't ripping you off.
We are simply dividing the increased cost of maintaining our Part M approvals (over that of the previous M3) and increased required maintenance data between our customers. Our CAMO fee charge is set at £200 per year with the maintenance same as before: Star Annual (ARC issue) followed by two Annuals (ARC revalidation), then it's back to a Star Annual etc.
As has been said, we aren't actually doing much more than we ever did (few extra sheets of paper to fill out) but the approvals do cost more. We don't need any more staff - loads of overtime setting up the approvals initially and getting to grips with the new paperwork, but next year should be much easier.
The maintenance company will be JAR145 or Part M Subpart F - they do the actual work, the CAMO is a Part M Subpart G organisation (with 'I privileges' if they can issue ARCs in house). The Subpart F and G organisations may be the same company or they may be different ones.