There are all kinds of good prices on both lowers and ammo right now.
PSA is selling complete lowers for under $140. And deals on ammo are out there. Mainly online, but if you're patient you can find them pretty frequently.
I agree, I love PSA and cheaper than dirt has good prices on ammo. Got 1000 rounds of .223 for less than $250 after shipping. It's not the best but got for practice.