Two things....you have security at the gates. That costs a lot of money. Any time an HOA has people involved...concierge, security, watchman, gate attendant or whatever you call it, the HOA dues are significantly higher. Also in gated communities the residents are responsible for street maintenance, not the city. Lots of foundation problems in this area so not only does that affect the homes, but also the streets and they are expensive to repair.
You can see a list of homes for sale in Hackberry at this link.