The construction jobs come from building out the space and necessary infrastructure upgrades are paid positions that often are contract. They aren't permanent but they count for additional tax revenue. As is the revenue of the jobs created by the spending from the additional HQ2 positions (25k jobs requires X new lunch locations, Y new fitness trainers, etc). That is the halo effect.

But do we think the jobs that the new Amazon hires are vacating will go away? Seems probable that many of them will be backfilled, and potentially at a higher compensation rate than they were before, since there'll be more demand for software engineers in the market after Amazon has moved in.

But if those other companies then have to fill the vacuum by hiring even more, then it's still a + per job; and arguably more because increased liquidity in the job market results in more competitive salaries.