I have a background in mechanical design (and I'm a miser...bad combo) Trouble is, when dollars go down the weight goes up. If looking to make a set for a 250 pound boat you move yourself, you may be able to come up with a decent combo. I came up with a design that uses electrical conduit & fittings and golf cart wheels/tires. Largest expense being finding larger diameter tires.

The bearing surface is the key, a H16 or heavier boat is hard to move without "nice" bearings.

ps Where's Doug Snell when you need him? He must have posted that ho-made set made with the blue barrel at least 1,500 times on every cat forum ever known to man. ps