Budget for any project is allocated right at its initiation phase. Budgeting includes lot of factors but the main factor remains customer defined timelines. Keeping this target defined by customer in mind, a backward calculation is done and accordingly time allocation to each phase is done, team sizing is defined and resource planning is done. After all it is customer that matters the most.
Well, it does not mean that there is a scope of comparison even if this backward calculation is being done. Two prime factors that play a major role in this whole game is quality and finances. Budgeting beyond optimum level and compromising with quality of the product will mar the beauty of product and impact on business badly. When timelines are shorter there is another way of pulling your socks and not letting you beaten down. It requires higher level of skilled task force, error free tools and rich experience to win over in such kind of wars.
http://itknowledgeexchange.techtarget.com/quality-assurance/all-projects-face-budget-constraints/