All prices approximated.
10 point roll cage 1.75" modified "swing-out" components for the seating areas, quoted nearly $700 installed for chassis tie-in, etc. and certification, and because it's for a 4-door.
Helmet = ~$200
Kirkey Racing aluminum seat and cover = $180
Simpson racing harnesses = $130
10lb Halon Auto Firesuppression = $319
RCI, SFI 3.2A1 spec jacket = $89
so, all said and done, misc. crap like remote battery disconnect, roll-bar padding, etc. will probably put me at around $1,000 or so, not including incidentals.