When I first wanted to get my boat painted, the quotes were breath-taking (including in the St Pete FL area where is home-base). I tried to 'negotiate' a bit with "Ya know, this isn't the Russian Winter Palace. I can survive a few blemishes - doesn't need to be perfect." Nope - all the yards said they didn't know how to do a sub-par job, didn't know what corners to cut, wouldn't do a job they woundn't stand behind.
The amount of prep work cannot be overstated. I can't tell much about the OP's pic from his avatar, but would not be a bit surprised to find there is 125+ man-hours in prep work. If there are fiberglass repairs needed - say fill-in a hole where an old depth meter was, and price goes up of course. Some hardware needs to be removed, some can't be so is taped around, and may need to be taped several times through the prime-paint coats. Non-skid areas are done separately. Depending on the yard, some sort of "spray booth" is needed - either a garage or a temp one built around scaffolding. Takes a lot of space too.
The materials alone will run a couple grand - I just picked-up a gallon of AwlFair (fairing compound), a gallon of AwlGrip paint, and a gallon of bottom paint. At wholesale pricing (no tax), with catalyst, was a shade almost $1400.The amount of sand paper discs is staggering. Easily around $2k when done for paint and consumables.
I am not going to defend the high cost of a paint job, but I can explain it. In the end, DIY vs professional can be a lot less expensive. Having watched a LOT of boats get painted the last year or so I can tell you that it takes less than a day to spray a boat - all the labor is in prep and final buffing.
That said, I watched a very festidious couple paint their 45-foot sailboat with Brightsides. It took them about 6-months working weekends and it looked very good when they were done. You had to look pretty closely to see the blemishes. I saw them 10-years later and their boat still looked pretty good.
Peter