There is no single Europe-wide daily cost. A slow trip through two regional cities can cost less than a rapid circuit of major capitals because every move adds fares, transfers, and sometimes an unusable half-day or extra meal out.
Build a low and high estimate for each category, then add 10–15% for price movement and small omissions. Use live supplier prices before booking; editorial estimates are for shaping the trip, not guaranteeing a final total.