The cita previa bottleneck
The cita-previa appointment system for NIE, TIE, and most immigration steps in Madrid, Barcelona, Málaga, and Alicante empties within seconds of slot release, and a scalper market resells appointments for €100–400. This is the structural condition of the system in the big cities, not a temporary backlog. A gestor is the practical fix; Las Palmas, Bilbao, and Zaragoza are far easier.