Depending upon your car's mileage, how you drive the car (stop the car against bump stops in parking lots), and how rough the roads are in your area, this is not out of the ordinary. Car do not go out of alignment by themselves. They go our of alignment because parts wear, bend, or break.

I can't speak to the amount of the quote, but the fact is that you probably went to get an alignment on someone's recommendation, or your because of your own observation that something was wrong (car pulled, tires wearing badly, etc.).

So, if there is something that has gone wrong, such that you need an alignment, then you should be glad that someone found the originating problem.

In fact, the problem opposite what you are suggesting, is more usually the case. More usually, a repair show will "align" your car without consideration of the suspension componenets and you end up not giving you the benefit of the fresh alignment.

Unless you have some other indication that this dealership is ripping you off, I'd try and look at this positively.