no. stop. the evidence is in front of you. he's asking for $10 billion dollars, without any sort of serious costing. all professional estimates suggest it's going to cost more like ten times that to build an actual wall.
if he was serious, he would be staffing a committee to figure out how much it's going to cost - to start. obviously? but, he's not. because he's not serious.
10 billion dollars sounds like a lot of money to you or i. in the context of the american budget, it isn't. and all it's going to actually succeed in building - after many years of delays and waste, no doubt - is what i've described.
you can call him incompetent if you want, but in this case you're actually being deceived.