My guess is total cost would be around $1,600.
You'll need a new barrel that can accept the suppressor - $250
Decent Suppressor - $800
Trust - $350
Stamp - $200
NICS - $5
Might be less for a .22. I never saw the point of a suppressed .22, though. I think suppressors are cool. But, it's just enough money and hassle for me to still not have one. I did the drill to get my one machinegun. PITA. That was enough for me.