So you’ve been using Halion for 4 months? (your post is kinda hard to understand…)
Sorry but if you’ve been using it for that long (or even 2 months) then you don’t really have a case here. Even if they decided to give you a bigger discount for complaining that you bought Halion recently, they would look at the date of purchase and tell you that they can’t do it.
Again, remember that you can take advantage of the deal now (by buying Absolute 3 alone, don’t upgrade your Halion 6 license) and sell your Halion license in the future. You’ll most likely end up getting a better deal than if you hadn’t bought Halion 6. Someone at KVR was able to sell theirs for 120 bucks in a few hours.
As for Cubase Pro upgrades, keep in mind that the upgrade price for each individual version (50 to 100 bucks) is far lower than most other DAWs, which is around 200. Even if you skip a few versions, you would be paying the same or less than the price to upgrade other DAWs. You can upgrade from the 6 year old Cubase 7 for 200. During this time, both the CPU performance and workflow have been improved greatly. Cubase almost feels like a different DAW now. Meanwhile Ableton just released an update for Live that adds almost nothing in comparison and costs 250 euros. 