Many people use New and Used Yachts for Sale - YachtWorld.com
. Just remember that the offer price is almost always higher than the actual sold price. The condition and what is included can affect the price a great deal. A 20 year old Catalina 30 in decent condition can be 10,000 or less if worn with an atomic 4, and as much as 15 to 20,000 if it is in great shape with maybe a new engine, good sails and and a dink.
You will see huge differences in price.
If you confine your search to the same model and approximate age you will quickly get a feel for what is a reasonable price.
If you are looking at many different brands you have to look at a lot more boats to get that feel. A Sabre will always fetch more than a Catalina for example, age condition etc being about the same.
Once you get a little more serious and you "loose" some boats your broker can go on soldboats.com (you need an account) and tell you what the boat you looked at actually sold for. This is not gospel however as many brokers are known to fudge numbers and with the complexity of the trade-in's and fancy deals the actual reported price may not always be as it appears.
Whatever else you may be an expert at, cars, houses etc. this is the same in some ways but different enough to take significant time to be good at identifying a bargain.
No book or website will do more than just give you a very general idea of where the price should be.
The condition and gear varies so widely from boat to boat you have to get to the point where you can do the calculations yourself.
And this is just the objective easy stuff to figure for example.
Boat A: +5,000 for 3 year old engine -6,000 for beat sails
Boat B: +3,000 for 1 year old canvas and cushions -2,000 for hacked wiring
Then you could figure the subjective stuff like:
I call this stuff subjective because someone else may weight things differently depending on what they like, intended use and skills.
Boat A: shoal keel +2,000 PHRF above 180 -1,000
Boat B: Fractional Rig
: +1,000 Trashed interior +4,000
The plus 4,000 for the trashed interior is because the bad interior is reflected in the price. For me since I'm going to cruse with only two people I plan on making changes anyway to create more storage space. I'm a skilled wood worker so for me a boat with an interior that needs work is less of a problem than to most people.
This is just an example of a subjective calculation.
The bottom line
however is that after all these calculations once you fall in love with a particular boat you will mangle the numbers until you convince yourself the boat is a great deal and the only question left is how to pay for it.
The heart usually wins over the head.
There are some tricks to try to overcome this problem but they are not 100% effective.