Imbel kits are available from Enterprise at around $300, others on falfiles and gunbroker may have them for slightly less - usually around $250. Inch kits should still be available from Interordnance and possibly a couple others (try Copes or Centerfire), less barrel, although US green mountain barrels and surplus ones are available. Total price for kit and barrel will be similar to the metrics. Sarco also has metric kits available, haven't seen them but heard they are Argentine, for around $250 too. Contrary to popular belief, kits can still be imported, but not with barrels. Given the current election situation I don't know which I would get first, but kits can be stopped quicker than US receivers.
The only receivers currently being produced are Enterprise, DSA and Century. Haven't built on Enterprise so can't comment. DSA is great, but pricey and tough to get. Century used to be bad, but the new ones have been in spec and work without issue. Downside is right now I think only Inch pattern is readily available, and the metrics are type 3 only, plus resale value will be lower.