This has been a great thread for me because I'm currently scheming how to lift our ~ 1300 lb, 19' boat up off the trailer so I can lower the keel for antifouling. This thread reinforces my plan to drive the trailer onto wheel
ramps, erect jackstands or homemade frame under boat, then use jacks to raise high enough, and remove wheel
ramps to lower the trailer... and reverse this to complete.
To the OP, yeah it seems that the cost of hoisting and moving the boat kind of wipes out the savings, doesn't it? A hydraulic lift boat trailer with pads is the easiest and fastest way to move the boat - no cradle required - but probably too expensive to consider.
If you could somehow build a decent cradle (wood and/or steel) under the boat where it sits, you can then hire one of those flat-deck car haulers (truck or trailer) and winch
the cradle + boat onto the deck