We currently do not have a way for authors to create coupons. However, there is a solution that you’ve already alluded two. Basically, you’ll need two versions of your book – one public with your marked up price and one private that’s only available to those that contributed to your book. 

To create two versions of the book, you’ll simply need to upload it twice (start the upload process by selecting "Order Book" in BookSmart). Then, go to your "recently uploaded books" area, and then the Book Detail of each book. To avoid confusion, you may want to give both books slightly different names by choosing "edit" in the Summary area.

Before either book is available to others, you’ll first need to purchase a copy yourself (which is unfortunate in this particular case, but is how the ecommerce system has been developed for other reasons).

Finally, once your private book is ready, you’ll need to "announce" it to all your contributors – this will give them a special link via email that will allow them to access the private book. To do this, go to the private book’s detail page and select  the "Announce" icon found right under the picture of your book’s cover.

Hope that helps,
Jack

I just got the answer to my own question: "How long is Blurb going to wait before they offer authors the ability to create their own discounts and coupons?"

 The answer: Forever.

Blurb has no plans to offer this convenience. It’s a shame, too, because so many other online order systems have this ability. Smugmug.com, where I sell my photographic prints, offers discounts. Spreadshirt.com, where I order my custom t-shirts, offers discounts. But Blurb doesn’t. Welcome to the Stone Age.