Most supercharger kits including the Harrop kit are $6-8,000 with a tune uninstalled, so probably $7-9k installed. Gears alone are around $2.5-3k installed, with lockers that jumps to around $5-6k. There's trade offs for both and having re-geared vehicles in the past there is no replacement for displacement, if you felt your vehicle was gutless stock and you add gears and 35's it still going to be gutless. Personally to push 35's I'd rather pay the supercharger fee. If I'm spending $3k for gears and I can get a supercharger kit for $7-8k I might as well go supercharger cause last time I re-geared I kept eyeing the supercharger anyways. Comparing stock tires to 35's it's only a 230rpm difference in 6th gear @80mph in the end, with our torque curves you're talking a 20-30Nm gain at the engine when you re-gear. That's barely enough to really make a difference when a supercharger would net you 100Nm+ @80mph with no gear changes with a 30% gain in performance which is fairly conservative with this size supercharger. I've seen a lot of folks builds here...$7k is barely a dent in their spending on the rigs, clearly people will pay what they value, for me supercharger>gears all day long.