Dear Nicke,
I am going to go out on a ledge here, (and undoubtedly invite some criticism), but I think your estimate may be just a bit low. My husband and I are in our 50's and have reached a point where we have stopped sweating the bottom line in our adventures. If you are more budget-conscious or budget-driven, then I think that a reasonable amount would be more in the 35-40 Euro per day range average. Our routine tended to be a cafe con leche and a pastry as we left in the morning. After 2-3 hours of walking, we would have a second breakfast of cafe con leche, eggs and bacon, and a fresh squeezed orange juice (I quickly became addicted to these!). Please note that between Roncevalles and Santiago, we paid from 3 - 9 euro for the same breakfast of two eggs and 4 slices of bacon and some toast. Fresh squeezed OJ varied between 1.5 to 4 euro...By noon, we were more than ready for a beer and a bocadillo - and sometimes we bought for fellow walkers.
By late afternoon, after we had settled into our albuergue and had washed ourselves and our clothes, we gathered with friends and imbibed and snacked some more. Sometimes we even paid to have our laundry done so that we could spend more time with friends. We met many younger pilgrims who were on a tight budget and as a result we happily pitched in more than our share of the dinner check. When they objected, we humbly countered with the simple request that they pay it forward when they reached our stage of life.
When we weren't walking and eating and drinking, we visited churches and museums and paid entrance fees and lit candles and tossed coins into the hats of those busking their way. We bought trinkets that we didn't need from children along the way, we tipped more than most would consider acceptable, and our returns were so much more than our investments. Some days we even treated ourselves to a private room to spare the other pilgrims the power of my husband's snore.
Some days are cheaper, some days are more expensive. Some people are more in the position to leave more behind in gratitude of what their lives have become. We spent hundreds of dollars on high-tech gear, and yet we met a lovely girl who just threw what existed in her dresser drawers into her pack. Sometimes the people you meet along the way are not quite there yet, and if you want to enjoy their company, compromises must be made.
While you really can do the Camino at whatever price point you decide, to cover the basics I would say 10 euro for your bed, 4 for breakfast, 5 for lunch and 10 for dinner (with wine), so almost 30 euro with no additional fun, is as cheap as you should budget.
As far as flights go, I have found skyscanner.com invaluable for planning and booking flights. They provide insight into routes and airline combinations that you may have not considered. They saved me over $800 on flights from Denver to Lisbon for our last trip, and over $900 between Denver and Madrid for Caminos 1 and 2.
Buen Camino and happy budgeting!
(retired), but I don't really care: I spend what I want, but these figures are what it is boiling down to for me.
