Hello fellow pilgrim,
that depends.
- when you will travel
- how do you travel
- where you will lodge
- meals as self-catering, pilgrims menu or "à la carte"
I did walk in July and had expenses for the whole camino just around 940€.
Transportation: 160€ for the flight to Biarritz, 180€ for the flight back from Porto, 12€ for the train from Bayonne to SJPdP, 3,20€ for the bus towards Leon, 39€ for the bus from SdC to Porto.
A mix of commercial, Donativo and municipal Albergues. A mix of no meal, self cooked and pilgrims menu.
No Hotel or Hostel.
In fact: you can do it for around 20€ per day. I did walk 27days and did it for around 17€ per day.
If you are very fast and have trained to walk more than 50km per day in rough terrain you can do it in 16-17days. If you want to enjoy your Camino, walk your pace and it will be anything from 20 to 60 days.
Transportation and accomodation are the two biggest parts of the total amount.
All in all it was cheaper than I first thought it would be.
If you tend to have more luxurious accomodations and want to taste the different local offerings in Restaurants you have to be aware that you are going to spend 50-100€ and more per day.
Hope that helps.