That is an excellent deal for new German magazines.
The POF magazines work really well too, but fit inconsistently in the gun; some fit normally, others are tight, while some are way too tight. The complex metal forming around the magazine catch area of the MP5 magazine results in an unwanted protrusion of metal on the POF magazines. This protrusion is variable in dimension, with some magazines having it worse than others. That protrusion rubs the inside of the magazine well, resulting in varying levels of binding.
The German MP5 magazines do not have that manufacturing flaw, and have a consistently good fit in the gun.
My assessment is based on six German "date coded" (mid 1980's) magazines and six POF magazines from RTG Parts, tested in one MKE Z-5RS.
I gave $30/each for the POF magazines and $50 to $55/each for the German magazines. I'll be selling the POF magazines at some point, while the Germans are keepers. At $50/each for new German magazines, I would say it's "FO TIME" if you want any MP5 magazines.