As a coming costumer at TF I find those "extra prices" far to high for 6 months.

It's fair enough to want/need to be payed for giving support more than 6 months, but why does TF have to shovel in 30% of that (maybe hard earned) money?

Let's say a "good" theme costs 53$ - 38% of that is approx. 21$.
I would consider giving that extra for eg. 3 years of updates" (if any), including "fair" support (beginners help for 6 months, guidance for the rest of time)

3 years is almost "forever" in the internet world (as in "life span") and time anyway to "look around" to maybe check out something new.

Clear rules, sellers can offer costumers to pay that solution or not, devs get more money etc.