You can buy 14' fly J sailboats with trailer for $500 once in a while, or all the time for $1000.

Obviously it's not some keeled ocean going vessel you keep at the marina.

But let's use your version.. a tiny boy scout dingy you can lift by yourself and put in the water. Should it cost $40 to put that in the water?

No, I agree: a boy scout dingy should not cost $40 to put in the water. A more serious boat, however, I can understand needing higher fees to pay for whatever services are used there.

Who the heck would launch a "real sailboat" on a reservoir?