No matter how much in demand your vendor may be, there are still always ways to cut costs: like having the wedding on a less-popular Friday night:

Understand who you are wokring with: Find out what other vendors offer for the same price point, and use this as leverage. See if costs could be negotiated if other vendors offer the services at a similar price.

Stick to your budget: A vendor may be willing to cut you a deal as long as you agree to something additional -- for example, he might consent to give you an extra hour of shooting, but only if you have him take your engagement photos. What you need to ask yourself is whether this will actually cost you more in the end.

Be friendly, yet firm: There's no harm in politely asking for a deal. If vendors are excited to work with you, they may be more willing to come up with creative solutions.

Hope this helps!

XOXO
Lorena