I replaced all my spark plugs, but it's still misfiring. Any help please? Could it be my coil packs? if so how much does it cost?

 

Most likely just 1 coilpack. Buy one and and start putting it on 1 cyl at a time till the misfire goes away.
U can get them for like 55 bucks

 

rockauto.com has them for $35 - $50 each

 

this. and make sure to reset the ECU after u find out which coil is bad.

 

exactly what plugs did you install? NGK Iridium? were they about 8 dollars each?
are you getting multi cyl misfire codes?
thats usually 1 coil bad as said above
did it miss before the plugs?
have you done the egr port/passage system clean yet? that will cause a miss

did I come in on the middle of this story -already in progress? any backstory??

 

when doing the try new coil on each cylinder (start with ones listed by codes)
reset the ecu after each coil movement

if doing the test method of remove the power lead to coil and ck for rpm drop or no drop, you dont have to reset ecu- just plug wire back in tight and remove next ones till the rpm doesnt change = the dead one