You'd have to ask at a few shops as they all charge different amounts. We don't get involved with costs here.
The jury is still out on the value of transmission flushes. About half of us don't believe they offer any value and half of us believe they're a great value. A simple fluid and filter replacement replaces about half of the fluid. That's enough to replenish any additives in the fluid that may have worn out, and we get to check for metal filings and other debris in the fluid. This service leaves half of the old fluid still in there.
Flushes replace all of the old fluid after running a detergent through the system for a few minutes. Some of us believe that detergent can tear some of the friction material off the clutch plates on those with very high mileage, leading to an earlier transmission failure. For this reason, I don't recommend a flush as a part of regular maintenance. Do the fluid and filter service instead at the recommended intervals.
My opinion is to do a flush when it is necessary to remove severe contamination. The common example is when the transmission fluid cooler built into the radiator springs a leak. That allows antifreeze and transmission fluid to mix. Transmission fluid in the cooling system will rot heater and radiator hoses from the inside and lead to an eventual rupture. Antifreeze in the transmission is much worse. Antifreeze will melt the soft outer layer of metal on the bushings. That leads to vibrations and eventual internal fluid leakage between parts that have to seal against each other. That will lead to the need for a total transmission rebuild. Preventing that damage is a valid reason to have the transmission flushed right away when that contamination is found.
A lot of people have flushes done in an attempt to solve a problem. The only problem that can solve is a shudder caused by using the wrong type of transmission fluid, particularly on newer car models from around the mid '90s on. A fluid and filter change will also solve that problem. Beyond that, most transmission problems are caused by something mechanical breaking internally, or an electrical problem. Flushing the fluid won't fix either of those things.
Here's a link to an article that might give you more ideas:
https://www.2carpros.com/articles/how-to-service-an-automatic-transmission
Sunday, March 1st, 2020 AT 5:16 PM