I had to purchase from several different sellers on eBay and Amazon to complete this set. It cost over $200 for just these books. I also bought a bunch of other rare Star Wars books. The Missions books are a junior reader series by Ryder Windham and Dave Wolverton (both very prominent Star Wars authors) that were distributed exclusively through mail-to-home subscriptions that you could only get from school book fairs sponsored by Scholastic. The series had 20 books. When you subscribed you got sent a tabletop game, a short story, and a game guide book based on that story. And then another story and guide book once a month every month for 20 months. It was canceled early and the only people who got all 20 books were the ones that newly subscribed and checked the option to send everything released so far (which cost more money). It canceled around month ten so books eleven through twenty are extremely rare. Some copies were $45 by themselves. Issues 16, 18, and 20 are exceptionally rare.
Star Wars did four more book series like this but only two more were the monthly subscription kind. The last two were simply sold in stores. Same Author though. Ryder Windham did almost all of them. They're not the ones I just bought but I probably will. They're all by Scholastic and Scholastic despises ebooks and refuses to ever republish any of their stuff on ebooks even though almost every single other (non-young reader) Star Wars publisher released ebook version because it's basically free money. Of course fans will buy them. Like me. Anything I can buy on Kindle I have been. These physicals I'm getting because the longer I wait the harder they are to find.
I don't plan to ever sell them. Maybe the duplicates I got. I got them so I have them forever.