I have been considering a 3d printer for several years now and final part cost has always been an issue, combined with print times and strength of medium.

The move to stuff like reinforced nylon and RYNO seem to make it more attractive, but, still not strong enough for some uses. And, like mentioned, casting in epoxy resin is very expensive.

Have you tried embedding aluminum structural parts in the print in some fashion? Like threaded inserts or rails? My thought was to print recesses for such items. Stop the print, insert the metal parts, then continue printing over them.