I am positive there is an old Tetris arcade cabinet somewhere with Mark's high score still on it!
For my M762, It was more cost effective to replace the axle than find bearings for the original one. New bearings were over 100, new axle, with everything but brakes (but has the flanges for it) was 180 ish. Uses standard bearings that cost about 15/side. Got it with 5 on 5.5 hubs to match the stock wheels, but could easily get 6 on 5.5 to match my wheels.
For wheels, I would have to match what is on my truck. Last time I purchased (5 or 6 years ago?) they were 80/wheel. Finding a used wheel is impossible. Tires are 250 each, that is about 700 for tires and wheels, mounted and balanced.
As much as I like saving money, I rather have new tires. My biggest example comes from JD's tire mishap in Rattlesnake Canyon. Americas tire, where I go, offers the free replacement for a small fee at the time you buy. If I buy used tires, I will be buying new tires to replace them soon enough after trail damage (which I feel is more likely on the trailer, since it can be controlled less in terms of avoiding debris on the trail and the road).
As for the fiberglass tub, I still rather have a steel tub. Trailers have a habit of sucking face with rocks and trees, and I rather be pounding out dents that cutting out damaged fiberglass and redoing it.