M&P Sport is about $620 street, Delton Sport is about $605 street and the DPMS Sportical is about $595 street. Those are the only three cheapies I would consider on a true AR-15 platform. You will be hard pressed to build them for those prices, especially if you have to buy the tools.
Accuracy comes from the barrel, upper to barrel extension fit and barrel nut. Reliability comes from putting decent parts together correctly. You can certainly get reliablity inexpensively. Accuracy is a gray area term. If you want sub MOA, you won't get it inexpensively. If 2 to 4 MOA is okay, you can get that.
Don't get hung up on the Mil-Spec mumbo jumbo, but don't buy unproven parts either. There is so much trash talk and marketing in this area that it makes it hard for the average guy to figure it out.
Bottom line, PSA makes decent quality stuff. If you want a very accurate AR, then you are going to be looking at $250 to $400 for a barrel.