My situation is a little different (traded parts, labor etc...), but expect to pay around $3500-6000+ depending on bags (coilover or bagged strut), install, tank size, compressors, fittings, management (manual vs. digital), etc. It can get very costly.
You can do it for cheaper by fiddling around with used parts and cutting corners here and there, but this isn't something you want to skimp out on.