Not that this will make you feel better, but I believe the training videos were made by Don McAllister who regularly makes videos showing how to use various pieces of Mac software and puts them in a podcast (see
http://www.screencastsonline.com). So at the time the podcast was made (and OmniGroup probably paid him to do that one), they had a coupon code to go along with it. Anyone who would go back and watch his earlier podcasts would see coupon codes and they're not still valid. Maybe OmniGroup should indicate the coupon code is expired on their website, but it still doesn't prevent people from seeing the video on Don's site without that notice.
I'm surprised you didn't get a return email or phone call as OmniGroup has one of the best support staffs I've seen. The few times I've contacted them, they always got back to me within a business day or two and sometimes within hours. Perhaps their sales staff isn't that quick.
Honestly, if you think the software meets your needs, I wouldn't let not saving $10 on $140 prevent you from buying it. While their software is a little more pricey than some competitors, they do make high quality software and support it well (bugs are usually fixed promptly and a reasonable number of new features are added before the next paid update). You get what you pay for.