Silly question? In a way, yes. It’s a bit like asking how much should you pay for a car. The answer of course is, it depends on exactly what you want. But if you ask the car salesman and tell him what you’re looking for he will give you a price. Not so with many web developers.
Call around a few web development companies, give them an idea of what you’re looking for and ask them for a price. I have done exactly that when I got my assistant to research my competitors’ pricing and she got various answers ranging from “(sharp intake of breath) it depends what you want” to “how long is a piece of string?”.
The only company that impressed her was one that was able to answer straight away with a price and then follow up with a few alternative options with prices.
There is absolutely no reason why web developers can’t give prices up front. There is no black magic in web development. You’re not asking these people to invent a cure for cancer. It’s a pretty straightforward process and there is no excuse for not being able to price things up front.
Not doing so is simply lazy and will turn away most potential clients before they get through the door.
If you come across a web developer with this kind of approach just walk away.