I spent years looking for those pipes when restoring a K8 I bought new, and a K7 my son rode. My best buddy restored his K8 at the same time. He got frustrated and bought a repro set that cost him $1500 plus shipping! I bought mine one or two at a time and typically paid $200 for a really good (or even a few NOS) singles.
Problem is, most of yours look blown through..... that usually means the baffles are loose inside too? If you were local, and one is really good, maybe $250 for the set (Max). Also, the two brackets that locate the pipes to the rear foot pegs are unique to K7/8. Even with the repro pipe set, they are a “must have” and getting very tough to find. $75-100 for the pair.