1998 Accord exhaust system-exhorbitant repair quote

Honda Accord EX V6 dual-exhaust 1998 111,000 miles. Dealer says the "b-pipe" is all stainless but it has a regular steel flange welded to it and the flange is rusted, so the whole pipe must be replaced ($574 parts & labor). PLUS if there is a problem re-attaching the mufflers, one or both may need to be replaced ($301 each for P&L). Could it be that this $1200 cost is legit? Why can't they weld a new flange onto the stainless pipe? (He simply says "they don't do that"). He also said the converter is fine. This car went from being quiet to very loud and a loss of pickup, so cannot drive it "as is" in my neighborhood. Thanks in advance for any help--web searches have been fruitless so far.