Do you think Zurich is "expensive" for its features and level of quality ? The scenery you bought for FS9/FSX was made more than 13 years ago, and we had to do a considerable amount of total rework to do it in MSFS, it's almost a complete makeover.
We did something like this with CYVR, offering a discount to existing users, and that was a scenery from 2013. We sent an email to all existing users, and almost a thousands of emails bounced back, because users changed their emails without alerting us. So we had to spent lots of time of effort to manually update emails and send the special offer discount to angry users that faulted us because they never bothered to contact us before to keep their emails updated.
And this was for a product that came in 2013. Zurich came out 6 years earlier, so I can only imagine how many emails would be outdated.
In fact, I couldn't not find any orders, ( both on our site and on Simmarket ) from the email you used to register on the forum, so I guess this would have happened to you, since you probably bought it with an outdated email. And, there's the added complication that Digital River removed all the personal details for orders older than 10 years, to comply with GDPR regulations, so all data for orders made in 2007-2008 was removed, and since Zurich came out in 2007, it means we lost track of lots of users for that reason.
So, to save us and users for all this hassle, we simply priced the scenery cheaper than it would have been, considering the kind of product its quality and its market appeal, under the assumption that, most of our users probably already bought it.