Counterintuitively, a private guided tour can save money on specific legs of this trip. The Marrakech–Aït Benhaddou–Ouarzazate day trip by shared taxi and local bus involves three separate fares, potential dead time waiting for connections, and no guide to unlock the context that makes the ksar worth seeing. A private day tour from Marrakech covers the same ground more efficiently, and when split between two or three people, the per-person cost is often competitive with the DIY version.
The same logic applies to anyone adding the Sahara to this itinerary. Public transport to Merzouga from Marrakech or Fes takes 8–10 hours, requires multiple changes, and deposits you in the desert without an included camp or camel ride. A private three-day Marrakech–Merzouga–Fes tour handles all of that in one package — at a per-person cost that, in a small group, compares favourably with the DIY alternative once you add up buses, accommodation and activities separately.