People are saying $9.99 is fair because they're used to paying $15 for a disc at Best Buy. Consider for the $15 at Best Buy you're getting cover art, a case and the disc provided. There's also the cost of shipping to the store, shelf space, air conditioning, lease on the building, paying the staff...
For $9.99 Wolfgang's is positing you provide your own disc, your own cover art (or expend your own expensive ink printing a PDF file) and make the disc with your own equipment, and still pay 2/3 of the price you're paying to the retailer. They have no cost for manufacturing, shipping, or production, yet charge nearly as much!
Sorry, put one more down in the $3.99 (or less!) column.
*Why won't this thing break up my paragraphs?!