One of the most difficult aspects of engineering is ensuring the requirements are satisfied without exceeding the budget.
There are two cases, the first is scope creep, where requirements are added. The second is polishing and refinement, where the product is improved continuously.
As a rule, scope creep is driven by the customer, and polishing and refinement are the pursuit of the engineers.
RIA offers such powerful tools, with little effort, that it is easy to push code farther than before.
The only solution is careful and cooperative management by all parties.