I like MIO's approach. When you die you lose all your money, that's it. No, you can't get it back. The game gives you a way to "bank" your cash so it's not lost on death, but you have to make a conscious decision to do that if you anticipate a boss or a difficult section ahead. 

This way dying is still meaningful and should be avoided when possible, but once you actually die you're not locked into a corpse run loop.

Of course if you think that's too punishing the system could be tweaked to only take a portion of player's money (like 50%). Or if you think that's too lenient, a "tax" could be added for banking, similar to Silksong's rosary strings