The brake booster itself will costs around $230.00 to $500.00 depending on the make and model and year of the car or vehicle that the brake booster is for.
And then labor costs can range from $150.00 to $300.00 so you might pay from $380.00 to $800.00 to have the brake booster replaced at a shop.
Of course if you can replace the brake booster yourself then it will be much cheaper but only replace the brake booster yourself if you know what you're doing.