PSA has their crazy daily deals. $150 for a complete lower to your FFL.
https://palmettostatearmory.com/psa-px9mm-billet-complete-classic-lower-uses-glockr-style-516447190.html
While it says "must use PSA upper" - no, you must use a glock-cut bolt. I'm using an Anderson upper w/ no dust cover or forward assist, a NFA barrel, a Spinta bolt (they often have bolt+barrel deals), and some cheap hand guards off ebay. Add an inexpensive dot sight and you are ready for a LOT of fun at about half the cost of brass case 223/556. And, you can often shoot PCCs where you can't shoot 556/223, etc.