Near as I can tell, you can't do separate descriptions, just a list of categories and prices, and then a single block of text at the bottom. nambroth's page has a pretty good example of what you can do with the format.

Howeverrrr...

The "description" section allows you to use any of the markdown formatting. So if you wanted to have something more custom, you could do something like

Class title: All Prices
Price Title: See below (you have to set a price here, could do $0, or could do minimum commission price.)
Description: [Custom price sheet, with headers, bullet points, other markdown formatting, and descriptions for every price option.]

You could also just have all the prices listed, as they expect, and then type out the descriptions as separate bullet points.

These are both kinda workarounds, but hopefully they'll let you do what you're shooting for.

Ah, jeez. But that does describe it pretty well, so thank you!