How much should a basic 340 rebuild cost?

The things that you mentioned are not important for a daily driver, who's concerned about what the pistons weight or if he's cam is degreed? I've put together several engines without having those things done and they ran fine for year's. Not everyone builds a high performance engine. For the purpose that we needed from a engine NAPA did great work, there was other machine shops that we used as well. Bore to piston clearance and bearings clearances were always good so the next best thing to do before putting the engine together is to be sure that everything is clean. Simple builds last a long time trust me on that.
Changing pistons may have the rotating assembly out of balance.
Degree of cam is for stock rebuild too.
Chain sets can be far off straight up. You want it in a bunch of degrees out retarded or advanced at what you think is straight up.