...why the -40% purchase before 2019 incentive for?
I think this is offered every December.
FYI, you have over a week to order with the discount and this includes the 30 day money back guarantee, if you aren't satisfied.
I couldn't get the VSTi to run in Reaper when I first received it, but with the help of Pipeline and a few others on this forum, I am up and running with it. (Much like the Reaper forum members)
Although more features will be added over time, it is a good start for now. And if some of the features you need haven't been ported over yet, you can still use BIAB and export/import tracks as before.