I am sorry but have to agree with some of the customers.
It also confused me, by making a comment 'X-Plane 12 update will be free', it is very easy to assume it is for everyone.
If you wanted to make exceptions, exclusions or restrictions you should of included this in the above heading.
For example you could of had X-Plane 12 Update will be free for new customers or those who purchased it after a certain date. Where is can EASILY BE SEEN!
Instead you left the meaning unclear and easily open to misinterpretation.
That said, I know you guys have put i a lot of hard work in upgrading the product (I know it is not a 5min job), and I along with many other people respect that. I know fifteen dollars is an affordable and reasoable price and I myself will be paying it, but I will do it with the view of supporting you guys and a thank you for your time and effort.