Wow, never had that happen. Were you both just not spending any money at all? I can't find any mention of what to do in this situation in the rulebook, but it seems unlikely you'd gain enough to wipe out the entire bank. You are paying the BANK and not the OTHER PLAYER when paying for extra resources, right?
My guess would be that the bank is unlimited and so suitable replacements should be applied (option 2 from your choices), but Bruno, Antoine or the publisher would need to confirm for sure.
1. Both players had many yellow cards
2. Player 1 has guild with 1VP for every 3coins at the end of a game.
3. Player 1 has economy token.
4. Player 2 has few blue/grey cards.
= for both players its optimal to discard for money many cards
my opponent had 21 points from 1 guild card(1VP/3 coins), he had 65 coins ( we used raplacment).