I tried building a sneaky from one of the under ten dollar budweiser cues years ago. New shaft, best of everything. New joint. When I played with it, it played better but still solidly in the junk range. The cue value didn't go up by the amount of components plus I had over half a day's time invested in turning a six dollar cue into a maybe $25 cue.
While components matter most on the tip end of the cue and least on the bumper end, I have proven to myself that even the bumper matters. Another issue, one low quality component brings the whole cue down. All components need to be in the same quality range. You can't turn a sow's ear into a silk purse!
Hu