The heart of a rifle its the barrel. The quality of the barrel and the treament it receives after manifacturing will affect the price. Many people will argue about which barrel maker is best, but I'm not going there. Metallurgists have well established measures of the various criteria to consider when making a barrel. So understanding those is important.
The bottom line is this: When I get sick I don't apply to medical school, I go see a doctor. He/she has been there.
My advice is get your criteria list together and then buy the rifle assembled by proffessionals. You'll get a warranty with it.
Every week there are AR for sale assembled by shadetree armorers
that I would't ever consider spending my hard earned money. They make outlandish claims of accuracy and then when you ask them to verify them at the range they loose all interest in making a sale.