During the 80's i became close friends with a guy who built a few tables every year. He also dealt used BBC, & Fisher coin tables, and maintained many of the local tables in a tristate area. He also built some bars, again both commercial and residential.
I came to understand over the years that all that frenetic activity from 4PM through early morning was in many respects therapy for his day job "for the gummint" & he died from stress before his time. But that's another story.
John had sought me out to make some curved molded bar rails for one of the commercial bars. From then on, i made wooden parts for many of his ventures, and then started making tools and tooling to facilitate his table work. Regretfully, i never paid much attention to the actual builds, always assumed "John would be there" if i ever needed a table. Plus his builds evolved as he experimented to make them better. He copied BBC including GC methods, but was always trying to improve. I went once with him to the quarries for slate, the van would haul 3 sets per load. I still buy architectural slate from the same place, but they sold their hone for pool table slates years ago & no longer offer that specific service.
I don't know enough to build a table from scratch at the moment & wouldn't know where to begin with rails, but i do know from close exposure that it is fairly basic woodwork, so long as there could be a resource for the specific details. A table boils down to a solid, stable platform for the slate. The critical parts are the rails and rail attachment methods. Parts most people would choose to buy are the pockets, irons, any castings depending on style (design)
For someone already in hardwood lumber trades, a table could be built from scratch for relatively minor costs, the lumber is probably in inventory anyway. However, from any perspective, there's plenty of old tables out there for rebuild that sell for about what a set of new slates cost these days. But i doubt most who would be interested in building have any notion of significant savings. It's a challenge, like any other, that appeals to a certain segment or interest base.
smt