We are working in an environment where customers give us thick requirement documents and they expect the technical team to do an estimation on the whole requirement. Once they receive our estimates, they can approach the budget team to ask for the money according to the estimated effort. They have been doing this for more than 15 years, and recently there have been some talk to move to a more agile process.
This practice of BIG estimation up front will be the first thing that they have to deal with among other things. The big question that they are trying to solve right now is "how can they advise the customers that we can't give them full estimates up front?" Agile process relies on simple, easy to estimate stories, where each story carries a certain estimates - well at least this is how stories are defined in XP.
Following XP principals, the technical team should not produce a big estimate up front, rather they should break up the requirement into stories. If this is the case, how can the customers get full estimates and ask for budget?
Is this where Agile process need to be tailored, or mixed with another practice to make things work?