Professional musicians train for years, get an education, work many events, and will often only work one event per night. You're paying, in part, for the musician's years of practice and investment in their craft, and their performance at the ceremony, cocktail party, reception and after-party creates a mood and energy level for your events. Talented musicians own the room, captivating guests, and reflecting well on you for your fine taste in unique entertainment that fits your style of wedding.
They'll advise you on the amount of time they need, and it may surprise you that performers for the cocktail hour actually need four hours to complete their set-up, performance and takedown.
Soloists and specialty performers may not be as in-demand as deejays and bands, so they may not be booked as often as those types of entertainers. Thus, they have to charge a bit more to make a living as performers. And specialty acts located far from your wedding's location will have to travel there and back, all part of their timed package.
For this type of entertainer and others, overtime will boost those prices, so plan well and invest in more time than you think you'll need. When the entertainers have your after-party rocking, you'll want them to stay longer.