Not unusual, marine places seem to assume boat owners are either loaded, stupid, or both. When I got my 2001 Challenger, it had a frozen F-N-R shift cable. Bought the part and brought it to a place to have installed. The quote came to $506!! I responded with shock and told them for that I'll figure it out myself. They'd already pulled the old cable out, so I told them since the work is mostly done I'll pay $200. They refused, put the old one back in (in total the same amount of work as replacing it) and sent me on my way.
Took me 2 hours to do the work, including a trip to the hardware store for loctite, and I had no idea what I was doing.
Either find an honest shop or figure out how to work on these things! You need a good back, Sea-Doo doesn't make it easy.