Cell sorting can be done cheaply, but cheap cell sorting is just that. For this you would want high-purity and low-contamination. The HIV pandemic is hardest hitting in places like Africa and SE Asia. Many of it's victims are extremely poor and do not have access to facilities who could manage this type of experiment successfully and at low risk.

The cell-sorting isn't the only expense either. The genetic manipulations costs quite a bit too. A cheap vaccine is still a better alternative, or better yet, social interventions, or a combinatorial approach. It is great to see this type of work pushing the envelope, but I think of this type of stuff more like concept cars. They always look awesome on the show room floor of Detroit, but you never actually see them driving around the streets. Maybe someday in the distant future, but for now, the victims of this pandemic need more realistic options.