Is cost for replacement plastic radiator tank $268.85 plus labor $172.50 fair?

This is a very reasonable price. It is on the low side of the Estimator if you use that as a range guideline. Be sure the products and labor have at least a 2 year / 24,000 mile warranty.

Check the Estimator on top of the page for your zip code. In different parts of the country, the prices are different as well.