For what it's worth, I flew a DJI Neo at 2750 meters MSL in Costa Rica. It was marginal. DJI lists the "maximum takeoff altitude" for the Neo as 2000 meters. The rated numbers are likely somewhat conservative.
That's the maximum service ceiling, higher than that and the drones ability to 'bite' the air (to produce lift) diminishes because the air becomes progressively thinner. Higher than the service ceiling: the motors have to work much harder.
You...