Plumbing contractor concreted in drain/water pipes box
I have just discovered that the plumbing contractor who built my house concreted in the area around the drain & water delivery pipes under my bathtub, instead of leaving it open or tarring it in. The drain started leaking, and the plumber I called to fix it can't fix it without removing the tub, which apparently was also set in concrete, and chiseling away the concrete. He's quoted me a price of $3200 labor and $1000 parts. The house is about 13 years old.
What responsibility does the building contractor and the plumbing contractor have to fix this, since they are the ones causing the high labor/extra cost? Can I expect the original plumber to fix this mistake?