What you actually pay for
Judgement: the daily call on route, variant and timing, based on the forecast and conditions you cannot see from a map.
Logistics: hut bookings, transfers and a plan B when weather closes a pass.
Local knowledge: the quieter variant, the better viewpoint, the hut with the best food, and the history and nature along the way.
Skills: many hikers use a guided trip to learn navigation, via ferrata or winter skills they can then use on their own.
When you can probably go without
Well-marked, non-technical routes in mid-season, walked by a group that is fit, can navigate and has hut-to-hut experience. In that case the guide is a comfort, not a necessity.
How the cost compares
A private certified guide typically costs a few hundred euros per day for the group. Shared between four to six hikers, or on a scheduled group departure, the guide often adds less per person than the huts and travel.
Related questions
Is it cheaper to hire a private guide as a group?
Usually, yes. A private guide is priced per group or per day, so the cost per person falls quickly with four to six hikers.