Whats the cost of labor to build a interior wall that's 8 by 15?

Question:

Answers:
There's a whole lot of things that could cause this to take longer. But for a straight wall; no windows/doors; no plumbing; flat, 8' ceiling; 2 electrical outlets (code requires a receptacle every 6'); easy attic access; and no surprises ---- 2 days labor to have it paint-ready.

If there's no attic access, figure another 2 hours to bring power in from an intersecting wall and patch that wall.

Add 2-3 hours per door/window (that's to rough it out, install and finish)

Per/hour labor rates vary regionally. But this will help you make sure that your not getting an inflated estimate of the effort.