The deadline
What does it cost to keep your Memories with Snapchat?
Snapchat does not publish prices itself and points you to the app instead. In the Swedish App Store, Memories Storage was listed at 29 SEK and Snapchat+ at 45 to 55 SEK when we last checked. Which storage tier each amount covers is not stated there. Check in the app before you buy.
Snap offers three tiers: 100 GB, 250 GB with Snapchat+ and 5 TB with Snapchat Platinum. But they publish no prices. Their own support page answers the question by pointing you to the app, so which amount covers which tier is something you have to read there.
In the Swedish App Store, Memories Storage was listed at 29 SEK (that is storage for Memories) and Snapchat+ at 45 to 55 SEK when we last checked. The App Store gives neither the storage tier nor the billing period for those listings, so treat the amounts as a rough indication and nothing more. They come from the Swedish store; what your own store says is something you need to check there.
Whatever the amount, it is a subscription, and it never ends. As long as you pay, your Memories stay; if you stop paying you have 48 hours to change your mind before anything above 5 GB is deleted.
It is a perfectly reasonable choice if you use the app daily anyway and want the Memories feature as it is. Being able to scroll back to the same day five years ago is genuinely nice, and a folder on a hard drive does not give you that.
It is a worse choice if all you want is to keep the photos. Then you are paying rent forever for something you already own, and you are still tied to whatever Snapchat decides next. The company has already changed the terms once.
There is no conflict between the options, by the way. Plenty of people do both: pay in the meantime, get the export out without rushing, and then cancel the subscription once the memories are safely on their own drive.