In wasabi and samourai, the coordinator charges a fee that obliterates the savings

In joinmarket, there is no coordinator (well there sort of is, but they don't charge anything), but other people won't be part of your coinjoin unless you pay them, so your savings get eaten up by that -- unless you become a market maker, in which case you get paid to coinjoin, which is awesome

I made my own implementation of coinjoin over nostr that is similar to joinmarket except you don't have to pay people to coinjoin with you. I figure people will want to do so anyway just because it gets them free coinjoins. You can check that out here: https://github.com/brilliancebitcoin/void

However, even this one doesn't result in any fee savings for someone who is spending via a coinjoin. They don't have to pay a coordinator or the other members of the coinjoin, but the transaction fee isn't divided up among all the members. Instead, the person who hit the send button acts as the coordinator and pays the full mining fee. So they don't get a cheap transaction, they pay the full fee for a large transaction, which more than eats up their savings.

I'd like to see a coinjoin implementation where anyone can announce their intention to do a coinjoin in like 24 hours or something. Then other people can register to join it if they happen to need to send some money around the same time frame. When the time arrives, everyone gets a cheaper transaction (because they share the fee) and they also get to be in a coinjoin for free. So win win!