35% is legal on front door windows. And ofcoarse it is illegal to tint the front windscreen.
On my old Stagea I tinted my front door windows to 20% (illegal, but seriously, what kinda cop is gonna do you for that) (besides apparently with their light tester thingy it comes up as 27% or something anyway, so you can just say it must've had a slight standard tint when you got them done to 35% )
Anyhow, I got my old Stag's fronts done to 20% to match the rears and it matched perfectly, never had any trouble with the law and it cost me $100 at Mastertint (perfect job). Its generally $100 plus or minus a bit depending on the company.
Tinted: