I see an awkward problem with the coupons.
The minimum coupon value is $9.99 (or its equivalent in other currencies with the pricing matrix).
Udemy almost always has a sale happening for $9.99 - $11.99 on all courses. I wouldn't want to give e.g. a $19.99 coupon for my course and the students wonder my "discount" coupon is more expensive than the standard public price.
Therefore, is there any other sensible strategy than to make all of your coupons either $9.99 or free?