I want to love this card. It feeds my munchkin brain in a good way!
In theory, even if you buy cards that are new for your deck, it will still be worth it if your original decklist features enough upgradeable cards.
For every 2 upgraded cards, a new card can be added while maintaining advantage.
If you want to have the highest experience advantage, you need 14 upgrade cards in a regular 8 game campaign. If you merely want to stay neutral or above, then you'd be able to add 13 card in the same scenario. That would make you gain 14 upgrade exp with a 13 exp penalty for adding new cards (which would still be net-positive).
This card rewards pre-emptive planning and deckbuilding and gives more experience very early on.