Work turbochargers.
Basic rebuild is between $350-$450 for complete basic rebuild. All seals gone through. Balancing of assembly. Sonic cleaning of parts. Price does not include if anything needs to be replaced.
If you want to upgrade to a new billet compressor wheel, billet backplate, billet 360degree sever duty thrust bearing, ceramic coated turbine housing, and have your inlet bell ported, it would be roughly $750ish or so.