I'm not sure I understand the point of the card...
Enabling Trash for Benefit, much like Rats. The +Cards and slight cost reduction on expensive actions is there so that it does something on boards where that isn't a thing (it also comboes extremely well with Prince, but that's neither here nor there). No, it's not going to be worth buying every time, but that's intentional. Not every card has to be a Rebuild.
If that's your intent, then the card really needs to be changed. Except for corner-cases like Farmland, to TfB with a bonus you need a hand with
- Obelisk
- A Village
- A TfB card
- A cheap action to trash
This seems...unlikely to happen often. *If* that's primarily what you're after here, I'd change the top half of the card to either: be a cantrip rather than straight draw, to drop the need for a village; or let it trash things itself.
So:
£4 Action - +1 Card/+1 Action. While this is in play, Action cards cost £4. This cost cannot be modified further.
or
£4 Action - When you play this, Action cards cost £4 for the rest of the turn. This cost cannot be modified further. You may trash a card from your hand and gain a card costing exactly the same.
I changed the cost-setting to an on-play effect for that case as I'm a little unsure on how the timing rules would affect the second part otherwise - would it be in play when an on-play trashing happens?
I'm not sure I like either, though. The first makes Potions irrelevant except for Vineyards, Philosopher's Stones, and Alchemists as every other Potion card would prefer an Obelisk. The second is just a more complicated version of "trash an action card, gain an action card" with some random-seeming side-effects. I'm not being mean here, but I suspect that Obelisk is going to end up in your "Failures and Mediocrities" thread at some point down the line.
[/quote]