Original vs ??? Off market

[pflaming]

I will be removing an entire set of original brakes front and rear and install discs. For the cost vs benefits and work involved I'm going to go all disc. What I find interesting is that original drums are expensive yet off market are a fraction of the cost. Are the off market parts that inferior or are the original that scarce?  

Whatever, once removed I will check them for problems, clean them then  list them for sale probably mid next week. Front driver's side drum and back plate shown in picture.