A wire is $25. A certified check is a few dollars. What would the exchange cash out fee be for that hypothetical $600K real estate deal?
If the seller were going to accept a P2P transaction, it would depend on which exchange you use and your level of trading. But probably around 25 basis points at that level. You would likely charge the seller a "processing fee" for paying in crypto if that was the case, just like is often done for credit card transactions.
For a crypto-fiat payment processor on the transaction (instead of P2P), around 1% to the buyer.
It's more applicable in high fee/tax scenarios, so for instance in Argentina, any money moving out is held for 30 days by the Argentine government, and taxed at around 30%. If you wanted to get money out of Argentina, or a country with similar protective tariff-like money transfer laws, bitcoin would be the superior way to do it.