Anything else of value with exclusivity like an additional catalog or early-access would go against their stated goal.
So, I guess this is similar to buying official physical merchandise like t-shirt or mug at a higher than market price which they cannot ship (legally) due to the nature of their service. Both parties know that the benefit they get doesn't match the costs and it is about showing support.
Yes, I wouldn't suggest or support anything like that.
One way this feels different to me is that while somewhere able to sell merchandise may have a range of items including some very expensive it generally wouldn't be suggesting I buy something every month and then offer an increasing % discount for paying 3/6/12/24 months up front.
So, I guess this is similar to buying official physical merchandise like t-shirt or mug at a higher than market price which they cannot ship (legally) due to the nature of their service. Both parties know that the benefit they get doesn't match the costs and it is about showing support.