My least favorite part of wedding cake consults is talking about the price. I've found that most people really have no idea about what their budget should be, and are reluctant to tell me what they have budgeted for the cake. If they even have a budget, that is.
I get a range of reactions when I tell people what the cost of the cake will be. They either take the contract and don't say anything, or they say something like "Is that all?", which just makes me think that I'm not charging enough! My favorite customer is the one who comes in and says "This is what my budget is." I can work with that, but playing a guessing game with people is no fun.
What you should keep in mind when you're buying a cake is that you can go two routes. The first is thinking that nobody eats wedding cake anyway, so why should you spend any money on it? So you go to the local grocery store or mass-market bakery and get a basic white cake that was probably baked off-site, frozen for God knows how long, shipped to the store and decorated by someone who isn't allowed to spend more than X amount of time on it. You won't pay as much for it, but you're right, nobody will eat the cake. That's a lot of wasted money.
The second route is realizing that good cake will be eaten, and that the wedding cake should be a good dessert, not just something that looks nice for the pictures. So for that, you go to a bakery that does individualized wedding cakes on a regular basis, pays attention to them, and bakes them especially for your event. That kind of cake might cost a little more than the grocery store, but it will be eaten. That's what's called a "good investment."
What gets me is that people will go to a chain restaurant for dinner and think nothing about paying $6 to $7 for a dessert that came from the food supplier three states away, but when it comes to paying for a good wedding cake they don't want to spend half that much.
You need to realize that the wedding cake isn't just something to look at, it's the dessert for your guests. All 150 of them. How much would the $7 frozen and thawed dessert from the chain restaurant be for that many people? If you're taking your guests out to eat, which is essentially what you're doing by hosting a reception, then you should buy them something worth eating.
All right, rant button turned off...
My basic advice is to do some research about cake costs in your area (every city has a different average price), then decide what your cake budget is. Don't be afraid to bring this up with your baker, preferably before you make the appointment. You'll save yourself some time and disappointment if a baker is completely out of your price range, or you can decide that you want to put some extra money into the excellent investment that is a great wedding cake!