It is the hardest question.
It all depends on the lot size, tree amount, tree sizes, hauling, disposal, gas.....
You get the point, why don't you be honest and ask your client how much they paid for the service last year... normally they will tell you the honest price.
And add a few bucks to it, normally they will change services because they had bad service (low price = bad service) or the last guy thought it was not worth working for that rate anymore so you _NEED_ to charge a bit more.
Just add to the argument that costs have risen, they will understand and pay you for the extra you ask.
Honesty always pays off.