K&K has a good reputation. I understand that they actually make some parts for Mercedes; ship them to Germany where they are "branded" as Mercedes parts; and then distributed throughout the world.
Metal stampings for old cars are priced curiously because they are not made continuously; there isn't a stamping press in Sparta Michigan (where K&K is) or in Sindelfingen that is continuously pressing out 190SL floor panels or 113 fenders. They are made in batches, sometimes years apart; once you set up the tooling, best to keep on stamping!
That batch operation, years apart, can result in some wild price appreciation as inventory depletes and gets replaced with new stock. So, some dealer paid $x.xx each for a fender in 2001, and prices it based on his cost and markup. When he exhausts his supply in 2006, he comes to find that his cost is now 3 x $x.xx and re-prices accordingly. This partially explains why you might find some wild price differentials. Also, and I don't know this, there is some "eastern European" stuff getting on the market.
Talk to Cheryl or Tim at K&K and simply ask them about their fender quality, and if it is something they make or buy. Do the same to Pagodenteille. Good vendors are happy to talk about their products.
Michael Salemi
1969 280SL
Signal Red w/Black Leather
Restored