Why is this area as cheap as most of Vista if it’s a much better location?

Because for most people this isn’t a better location. Getting to a freeway – particularly Interstate-15 – is a real PITA. It’s “better” for our OP because their job is nearby. If this OP wanted to pay a premium for location they could buy at Bressi Ranch in Carlsbad and bike to work.

For most people the Discovery Hills and Twin Oaks areas of San Marcos or the Rancho Del Oro area of Oceanside or the shadowridge area of Vista are better choices because of the easy access to Hwy-78. But those areas are farther from the OPs job and would create a bit longer commute.