Might be worth checking Airbnb if you’re staying several days, there can be some good deals. I also used travel apps to find some cracking deals on the occasional hotel.
I used Airbnb last year when I spent some time in Santiago. First occasion I think it was about €15 per night but this dropped on subsequent visits, when I dealt direct with the landlord, to €10 per night. It was basic but I had a room to myself and use of kitchen and washing facilities, location was great - not far from train station and just a short walk to the main areas. I was also able to leave some kit there when I left to walk the Ingles.
I also shared the cost of a night at an Airbnb place in Finisterre when I finished the Sanabres (my first Camino). I had walked the last couple of days with a Dutch chap (he had walked the VdlP), we had met briefly several weeks earlier and met again on the way to Muxia. We were both walking alone, and happy to be doing so, but sharing the final steps turned out to be just the right end to our journey and we rewarded ourselves by splitting the cost of a two bedroom flat in Finisterre. The primary purpose was to guarantee a good, quiet, nights sleep but having picked up some food and beers we also enjoyed an evening of fellowship reflecting on our Caminoes, what had brought us there and generally putting the world to rights.
That trip last year was the first time I had ever used Airbnb and it proved to be very useful. In addition to the times above, I also used it for a night when I flew into Madrid and a couple of nights in Ourense when I took some time out from my walk to meet up with someone very dear to me who was unexpectedly in Spain.
I tend to feel that one shouldn’t abuse the alburgues, My personal view is that it’s fine to spend an extra day or two whether as rest days or even to see a bit more of a place but I keep in mind that they are there for a purpose and that purpose is not to be a cheap hotel. They are there to provide inexpensive accommodation and hospitality to aid pilgrims on their journey, so if what I’m doing at the time falls outside that, I seek out an alternative.
With all that said, alburgues vary. Some are very much a vocational thing run on a shoestring, others may be more of a business. My experience has been on quieter routes than the Frances and most that I stayed in fell more into the former category which has shaped my attitude towards their use.