April 2022 Update: The formspec transaction lag issue and other API DoS issues in mods are actively being exploited to lag servers to promote a ripoff makeworld game that only accepts exorbitant bitcoin payments.
I'm really glad to see this getting revamped from the 2016 classic yellow green and grey cubes that are on many servers! I can't count how many times I've been greatful not to have all my money on me when dying on a long trek in the wilderness, or falling into a feigned friendly player's trap for them to hoard all my hard-earned tools food and armor.
I have run against a couple issues in the design of the transaction system, which become much more apparent on populated servers, and I've even been able to reproduce it in singleplayer on a fast machine.
The issue is that when depositing a lot of money very quickly, the server and client lags significantly. This is true of any server I've tested, and any denomination, whether depositing or withdrawing. If this is extreme enough, the displayed account balance jumps to the correct value once the lag subsides, then counts the wrong direction from the transactions you just placed, so it looks like instead of depositing 1000 Green, the number went down, which is worrying to watch. The balance shows the correct value after placing another transaction or exiting, but it can cause worry that things are not running as they should, and raise concern over whether their virtual accounts are safe to use in case of a glitch or corruption.
So, as a reconciled action (and having a shop that can supply thousands of individual notes on a very crowded server), I don't think adding a 1000x button is the solution, but instead seeking out something like caching, or a place-and-commit functionality that lets the player do large transactions all in one go. The answer could even be delaying the actions and batching them automatically using a timed buffer, or anything else.