There are a few considerations for any wedding:
Musical requirements - dance, cocktails, ceremony... perhaps all three. Increasing the scope/scale of your requirements will increase the price
Production - lighting and audio. The scope and scale of production will determine the ultimate pricing - secondary audio locations, uplighting, moving head lighting etc. impact the pricing of the production package
Travel / Logistics - If you are planning an out-of-town wedding there will be additional costs which could include mileage, permits, accommodations etc.