Welcome to the forum.
There are a lot of possibilities there:
- They could be upgrade versions, and to use, you would need own a qualifying, previous version to use.
- They could be academic versions, and you would need a qualifying student ID to use.
- They could be pirated copies, and besides probably not working, or not working well, your credit card will likely be compromised, as well as your computer.
It depends on who is selling, and what they are selling. Usually, if it looks too good to be true, it is.
Good luck, but be very careful.
I've never seen a legitimate reseller offer the software for any less than Adobe, at least not that much less.