For S&G, you can build on frames (bulkhead-like) rather than cradles, and it's not tough to give them some sort of temporary square top (bottom when inverted) to rest on any convenient surface. If you don't like kneeling to build, setting them on sawhorses is handy, and only a few moments with a level and shims squares everything up perfectly. It means that you work mostly on the inverted hull at the start, which seems a more straightforward build process to me. Of course, if you are working from someone else's plans, the way they suggest would likely turn out to be the easiest, since all the forming edges (whether internal or external) would be worked out to the proper dimensions.

Having said that, I built a 2' by 16' table for my S&G, resting on sawhorses. One sheet of OSB and a few 2x4's handled the job - less than $30. That lumber is going to get a new life as a strongback in the near future. I haven't decided yet, but I'm thinking of building it in something of a "T" or "I" form rather than the more usual box, to gain some more surface for the same lumber.

Someone here showed a strongback built complete with several electrical outlets included. Great idea, that. No more tripping and tugging over extension cords. That'll need to be part of whatever I do, along with some take-down capability and attached folding legs.

As for cost, consider OSB as the building material. Much cheaper.