It cannot be cheaper, other than by avoiding taxes and regulation.

Consider sending money from US Dollar to Euro:

Sane way: An intermediary (IE a bank) handles this. You give them USD and they give the receiver Euros. This involves some service costs and 2 bank transfers.

Because people exchange money in both ways, the banks need not run out of either Euro or USD. In the background there is the currency market, on which the proper exchange rate is haggled out, which takes care of imbalances in cash flow.

Crypto way: You give a crypto exchange (an intermediary) USD and they give you crypto. This already involves 2 transfers and service costs. One of those 2 transfers is a crypto transfer, which is much more expensive (IE uses more resources) than a bank transfer.

This is already more expensive and then you have to do the same thing again to cash out.

And then we are still not done. Say there is an imbalance in that more people transfer money from USD to Euro than vice versa. That means that crypto becomes more expensive in USD and cheaper in Euro. There's more demand in terms of USD and more supply for Euro, right?.

That creates an arbitrage opportunity. You can exchange USD for Euro, and then buy crypto for Euro to sell for USD. This closes the circle and puts everything back to the initial state. But to do that, we still have to exchange the real currencies. So now the markets bake the cost of exchanging currency into the crypto prices. At a guess, for some currencies (probably not so much Euro/USD), that would have a significant effect. I'm thinking smaller, poorer countries that send many migrant workers, who send money back home. These workers would not only end up paying the insane overhead of the crypto system, but also, still, most of the normal, direct exchange costs (if they relied on crypto).