I am not saying you are wrong but in this case it is over 10% of the asking price...LOL
or 5% of an engine repower you weren't expecting.
If you have money to burn, skills to fix anything you come across, and like repairing as much as sailing, then by all means, forgo a survey on a BIG cheap boat.
But, if money IS tight, and you don't have the money or the skill or the time to handle repairs you didn't have the skill to spot in the first place, then invest in a survey. It's better to lose $500 on a boat you don't buy than to scrap a boat you did buy, that you shoudn't have.
Having said that, there is a great list of inspection tips here, which after poking around yourself with the help of the tips, will help you decide whether a boat is even worth surveying.
In any event, a marina will want insurance and insurance companies want a survey, so unless you are on a mooring, you will likely need a survey.