Below market but house has bad cast iron plumbing

[Ben Crego]

Hi, I am under contract on a house for $252,250 off market. I’m about 20-40 below market depending on your comps. The house looks great and the inspector only flagged a few little issues; but I had a plumber scope it and he said the cast iron is terrible (bellying, corroded, etc). The seller is only willing to drop to 250. The 1 plumbers quote to do a plumbing replacement without putting all the cosmetics back is $14,000. 

Plumber had technical difficulties twice and didn’t record but two guys both said plumbing looks terrible. I worked with this plumber one other time on another property. He was very good and consistent with his google reviews.

What would you do?