A dedicated .22lr upper is starting around $600. I built a cheap upper for near the same price. If you have an AR already this could help with the costs. I opted for the standard upper so I can still shoot 223 in it (out it?)(through it?). I have had no issues with the CMMG kit so far. Ammo is 1/5 - 1/10 the price of 223.

I have heard the .22 GSG's are cool as well. I played with 1 but have not shot it. They are around $500 and are definitely cool looking.