Ummmm .... it depends.
Some of my tours have been quite inexpensive ... others have been quite expensive. It just depends on what we used for accommodation, where we ate, what other forms of transport we used, what we did for entertainment, etc. etc. etc.
For example, my 3-month tour of Australia in 2004 cost somewhere around $6000 including airfare, the 1200K randonnee I did in the middle of the tour, and all the usual tour stuff.
But a weekend tour to Pine Lake in Alberta in 2006 cost about $10 (each) for accommodation, and we brought food from home which we would have eaten anyway ... part of the regular grocery bill.
Our hub-and-spoke tours can cost about $200-300 for 3 nights accommodation, plus a bit extra for food.
It all depends on what we want to do.