I'm pretty sure if someone paid the full price in 2104 could have contacted Adobe to make an adjustment since the $9.99 became the going rate for all. Adobe must have had poor sales with the full price of $19.99 for new customers.
Adobe is not charging two different prices for the same product or product bundle. Technically they are different products bundles, where storage changes from 20GB to 1 TB. Now, that price difference may not be attractive compared to other products such as Dropbox.
The fact that Adobe was doing test by removing the $9.99 bundle is different than saying that they had the same product with two different prices.