They gave a discount from a made-up price to another made-up price. The "contract" is a pure marketing fiction here. You can condescendingly explain what a contract is all you like, but the point of contracts is to reflect some underlying reality of the parties that needs mitigation so that they can have a mutually beneficial relationship.

For example, apartments are rented with an annual price and a monthly payment because a) both landlords and tenants have a lot of switchover costs, and b) tenants want to avoid landlords exploiting the pain of moving by jacking their rent up after a month.

But this is just exploitative marketing BS. When you sign up, Adobe is not buying a physical server that they have to depreciate and would sit empty when you quit. They did not buy extra buckets of pixels that will now sit unused in a warehouse. If a person stops using Photoshop, both the the provider expenses and the renter benefits cease immediately. There's no legitimate reason to charge people a cancellation fee here; it's pure exploitation of purchaser optimism and cognitive bias.