First, we haven't. We have hit the point where the amount in the current budget request exceeds the economic damage. The estimated total cost of the wall would be somewhere between $15 billion and $70 billion, depending on who you ask[1].

Second, it still doesn't matter. Giving in to Trump on this matter would only show him that he can expand his racist policies again and again by threatening to shut down the government again. "Once you have paid him the Dane-geld you never get rid of the Dane."

[1] https://www.politifact.com/california/statements/2017/apr/28...