Nail salons charge the amount they do for the time it takes their manicurists and pedicurists to complete the stages of a quality mani/pedi, including soaks, massage, nail shaping, polish and protective layer applications, nail art and other applications.
The salon may offer an enticing bridal package giving you the use of the salon just for your group, plus catering and champagne as part of your VIP bridal nail experience, and pricing for mani/pedi's can be higher in certain towns and cities.
Think in terms of time needed to complete a mani/pedi, the cost of labor to understand the fees in this sector. A complicated nail art or French manicure may cost more than a single-color coating, due to the extra steps needed for those more decorative styles. And again, it's the quality of the products used and the overhead of the salon that adds up to the prices you'll find.