Private lessons with good teachers are expensive, that's kind of the way it is. Some teachers and studios are more expensive than others, so if you didn't shop around before that might be something to try. Still, I think the cheapest I've ever seen for a private lesson from a good teacher is $60/hour.
If you can learn what you want taking group classes, that might be something that will work for you. There are studios where you don't have to sign contracts or pre-pay for a whole bunch of private lessons or group classes all at once. See if you can find one that has group classes that run as month-long series. And again, shop around, because prices and quality of instruction vary, but when you're dealing with independent teachers you pretty much get what you pay for.
And finally, if you are a college student, see if your school has a ballroom dance club or team. That can be a very inexpensive way of getting lessons.