Well, it got posted in 'bug reports', but I don't think any one called it a bug.
As used in magitech, there is no problem, that is indeed as it was intended.
It's a 'problem' for modder's because it's not really what it say it is, it claims to be a 'discount' but it isn't a discount, it's a refund.
Modder's should be given the option of either behaviour (a proper discount, and a refund like the discount param currently gives).
Unfortunately we can't just use 'discount' and 'refund', because discount means refund already...