In this debate question both the fence parts and the wall parts are mentioned, the 7.3 billion dollars are for the Texas part alone.
3 minutes— https://www.youtube.com/watch?v=jEgJh-1i1Cw
Texas is almost 2/3rds of the border with Mexico, with a lot of hydrological and treaty concerns along the Rio Grande, and a lot of Private property owners on the border, unlike the other border States, where the Roosevelt Reservation Federally controls the length of their border.
Even this go round, where essentially price is no object, Texas won’t be completely walled off from Mexico. Indeed, most of the remaining unwalled (although heavily monitored, for now) portions will be in Texas. It is almost too easy to build in the other States, by comparison.