So, Borrow, or the way Donald is talking about it, makes me think that the token will leave your deck when you draw that next card. i.e. you get a 4 card hand 1 time for each use of Borrow. Does this mean that if someone buys a card from the Smithy stack on which I've put my +1 action token for Lost Arts, the token leaves that stack? That would seem to make LA way way worse though. So maybe, especially since nothing says they do, the tokens just always stay there until a card tells you to move them. But in that case, Borrow means you're drawing 4 card hands for the rest of the game, from just one use (of course, I guess after you use it the first time, you can use it every turn after for no penalty). Am I grokking this correctly?
Edit: And re-reading, I can't even get $1 per turn (without something to move my -1 card token somewhere else), just once total ever overall period.
"Once per turn" means you can only buy Borrow once per turn. When you do buy it, you get +1 Buy, and if your -1 Card token isn't on your deck, put it there and get +$1.
When you go to draw cards, if your -1 Card token is on your deck, you remove it in place of one of the draws.
The +1 Action token does not get removed by getting cards from the pile it's on.