These things are so hard to calculate because there are so many variables. Exchange rate is such a big variable. When someone says, "Oh, I only spent $4000 for four weeks, it matters greatly whether it was 8 years ago, when the Euro was $0.98, 7 years ago, when it was $1.12, or one year ago, when it was $1.28, or a year before that, or this August, when it was $1.43, or now when it is $1.49. I've made four two week trips to Europe in the last 5 years, and my expenses, in Euro/day, have been almost the same, €70-€73 per day, but my $/day, with exchange rate has been $78-$110 $/day.
Even if you state the cost in Euro/day for your actual expenses on the ground in Europe, what country are you traveling in? Considering low cost B&Bs and regional rail passes, Germany is the least expensive country in Europe to travel in. Even there, there is a difference. On one trip, I spent €86/day in Munich, €70/day outside of Munich. London or Paris will cost more than rural Italy.
Other variables: do you stay in hostels, or in family run B&Bs, or do you stay in 3-5 star hotels, in big cities or in rural areas? Do you only ride in 1st class, with a rail pass, or do you use regional passes? Do you fly, or do you rent a car? Do you eat in sit down restaurants, or do you "dumpster dive"?
Considering all the variables, there is no way anyone elses experiences means anything. You have to figure it out yourself.
Where are you going, how are you traveling (air, car, rail, walk)? There are website that will help you estimate it closely once you have defined your travel.
Where are you staying. Make reservations, or at least make a list of possible accommodations. That way you will know your lodging cost.
What about food? I have found that I spend about €20 per day. I don't eat extravagantly, but I don't scrimp. You can spend less on food, but not zero. If you splurge every day, you can spend a lot more.