I always think that the more vias, the more expensive. So I try to decrease the number of vias on my design to save money. But maybe the number of vias has a small influence on cost. For example, if I want a 5"x5" board, how much would it affect a design cost to have 600 or 300 vias instead of 100? Will the size of hole effect the price? What I talked is through hole vias, not buried vias.