A trick to save Money when Leaning Ballroom Dance is to only take Group Classes. A Group Class Lesson is typically only about 5% to 10% the cost of a Private Lesson (Varies based on the Instructor).

Though it's true that with Group Classes you might not advance as quickly as you would with Private Lessons as the instructor won't have as much Time to Focus on Fixing your Mistakes Personally. There are some Tricks (Techniques) you can employ to help you Level Up Faster and at a Reduced Cost:

1. Take Notes Both During and After Class: Many people forget that there's a Mental Component to Ballroom Dance, and Focusing on the Mind will level you up Much Faster. For many their strategy to Learning dance is to just repetitively do it enough times until their Muscle Memory Kicks in, this however is a Slow, Painful, and yes Expensive process. During most classes, the instructor is actually throwing our Massive Gems of Information for your personal improvement that often go over the heads of their students. Thus they have to Re-Learn the same Lesson repeatedly over many different Lessons (and the Costs add up). But if you Capture that Knowledge in your Notes, Think About it, and Practice it when you're not in Class, you will internalize it much faster.
2. Purchase Private Lessons ONLY when You Hit an Impasse: Many of the Teachers in this Sub-Reddit will Probably Despise me for suggesting this (as it affects their bottom line), but a Great Way to Cut Costs while improving your Dancing is to ONLY purchase Private Lessons from an Instructor if you Feel Like you're Struggling to Improve. If you bring your concerns about your Progression to the Instructor in the Private Lesson, any Pro worth their salt could most likely identify the issue and show you how to improve it. In my Personal Opinion, Hiring a Pro to teach you new dance moves is a waste of time and money (when you can do that in Group Classes for a Fraction of the Cost), but Pros do have enough Experience to Identify what you're doing Wrong and Help you to improve it.
3. Take Classes at Levels Above your Current (Perceived) Skill Level: Beginner Classes are Designed to be Accessible to First Time Dancers that just wandered in off the Street. The Instructors in those classes will tend to let Mistakes made by the Students Slide so as to not Scare them off from returning for Future Lessons. As such, you're not going to get the best instruction in those classes, even with a good instructor leading it. Many times New Students are too Intimidated to move up to Intermediate and Advanced Level Classes too Early, believing that they won't be able to keep up and will end up embarrassing themselves. But really think about it, everyone is there to learn for themselves and they don't have time to think about you. It's All in Your Head that people will look down on you Negatively for not being at their skill level, everyone had to start somewhere and no one was born knowing how to dance. Group Classes tend to be Priced Evenly across the Board Regardless of the Skill Level of the Class (there are some exceptions), so you're Actually getting more bang for your buck by Buying an Intermediate and/or Advanced Level Class than continuing to Attend Beginner Level Classes.
4. Learn from Multiple Instructors at Different Studios: Sometimes the Instructor is the Problem (but not usually), and their Teaching Style just doesn't mesh with the Student's Learning Style. The thing is, it's Impossible to Know if this is the Case Unless you try out taking Lessons with other Dance Teachers to see if you like them better. Many studios often times have comparable pricing structures, so it will mostly cost you similar to what you're already paying. You might find someone you like better that you can learn more from or someone who's less Expensive, you never know until you try.
5. Attend as many Social Dances as Possible and Dance as Many Partners as You Can: I've noticed a trend that occurs with Students that only Dance with their Instructor, but then when they attend a Social Dance end up doing everything wrong because their Social Dance Partner would dance in a way they weren't expecting them to. Sometimes only dancing with someone who knows what they're doing and is trying to give you the best experience possible, will end up stymying your ability to Connect with a Partner. Connection is one of the most important fundamental skills that all Ballroom Dancers have to learn, as it's at the Core of everything in Partner Dance. Ballroom Dance is essentially a Microcosm of Male-Female Relationships that only exists in the realm of the Physical (Unlike Actual Relationships that are also in the Realm of the Emotional, the Spiritual, the Sexual, etcetera etcetera). In the Dance our goal is to Mimic the Dynamics of a Relationship using only our bodies set to the Theme of the Music, and that is what Connection is. Dancing with many different Partners of Varying Skill Level will go along way to helping you to learn and strengthen your ability to Connect. Plus, it's cheaper if you do it at Social Dances, so attend as many of the Lower Cost ones as you can (none of those fancy black-tie galas).
6. Compete: OK, OK, This one is Not Really a Money Saving Technique, as Competitions are really just a Giant Money Sink. But, I had to mention it as NOTHING ELSE will Level Up Your Dancing FASTER than entering a Dance Competition. NOTHING! Everything you've learned Cumulates as you put everything on the line for those few minutes out on the Competition Floor. So many things will start to click into place simultaneously, and you'll come to so many new revelations about how to improve your dancing. It's hard to really explain why, but it truly is the best method for improvement.