How much does it cost to change gear ratios?

Just got a jeep wrangler and the only ratio readily available on any models other than the Rubicon was a 3.21 ratio. I want to get something for better power like a 3.73 or 4.1 what would that cost me?How much does it cost to change gear ratios?some carriers will not be able to go that high in gear but ring and pinion kits with all bearings and seals are 350-400 dollars and the labor is about 175-250 so if 4x4 its times twoHow much does it cost to change gear ratios?I agree, 300-400