Only by using multiple backup sets. That is, back up your entire system with exclusion of the files/folders you want to keep only one snapshot of in the long run, and then back up those excluded files/folders in a separate run (but it can be to the same repository) complemented by forgetting and pruning all but the last snapshots for that specific backup set.
In total, this is a complete waste of energy. Especially since you say that storage is cheap, and restic deduplicates the blocks of data that it backs up, what’s the point in the first place? Just back your stuff up and be happy - restic will only add what changed since the last run every time you back up.