I think it depends on what you are looking at in a sporran: basic or fancy. They are bags for the most part. On the other hand, the ones from Thorfinn are well made and have loads of features.

The place I see the real poor disparity of prices are the evening sporrans, especially the inexpensive rabbit jobs (v. pricey fancy cantle and unusual fur one). While I might like grandad's seal skin evening sporran with the silver cantle, it has more disadvantages than an inexpensive rabbit one.

Also, the place where I see a real difference is in the day sporran lines since they are just bags, which can have loads of neat stuff added on.