A brake fluid change (flush) is one of the cheaper brake services, and it protects expensive parts - so it is good value. Costs vary by shop and vehicle, but here is a realistic picture of what a brake fluid change runs.
Typical shop cost
At a shop, a brake fluid flush commonly runs roughly $80 to $150, depending on the vehicle, the fluid type, and your area. Cars with ABS that need a scan-tool-assisted bleed, or that take pricier DOT 4 or specialty fluid, land at the higher end. It is mostly labor plus a bit of fluid.
DIY cost
Doing it yourself costs far less - just the fluid (often $10-25 for what you need) plus basic tools and a helper or one-person bleeder kit; see DIY brake fluid change. The main cost is your time and care to keep the reservoir topped and bleed correctly.
Why it is worth it
Whatever the cost, a flush is cheap insurance. Old fluid absorbs moisture, lowering its boiling point and corroding the ABS unit and calipers from inside - see how often to change brake fluid. A periodic flush restores a firm pedal and prevents far more expensive corrosion damage.
Flush vs bleed on the bill
Note a "flush" (replacing all the fluid) differs from a "bleed" (removing air) - see flush vs bleed. A scheduled maintenance flush is what you want every 2-3 years. Pair fresh fluid with quality pads and hardware for a healthy system.