Quality, time, and cost are the three legs supporting the metaphorical stool of project management. Good project managers constantly work to maximize the outcome for a project in each of these three realms. 

The most difficult aspect of this nonstop challenge is that each of these priorities compete for dominance over the other two. Quality is surely easier to maintain if we relax our concern about schedule or budget; costs can be reduced dramatically if we let go of worries about quality or schedule; a schedule is easier to hold if either cost or quality are not issues. There are many situations in which a deadline is non-negotiable, for example, and if that creates a schedule that is highly demanding - maybe even unreasonably demanding - the stress on quality and cost control will be extreme.

"All projects are framed by some balance of emphasis on expectations related to quality, time, and cost." ~ Sam Rodell

The most difficult aspect of this nonstop challenge is that each of these priorities compete for dominance over the other two. Quality is surely easier to maintain if we relax our concern about schedule or budget; costs can be reduced dramatically if we let go of worries about quality or schedule; a schedule is easier to hold if either cost or quality are not issues. There are many situations in which a deadline is non-negotiable, for example, and if that creates a schedule that is highly demanding - maybe even unreasonably demanding - the stress on quality and cost control will be extreme.

In reality, all projects are framed by some balance of emphasis on expectations related to quality, time, and cost. If we refuse to prioritize them - if we take the position that all are equally important - we are effectively saying none of them are important.

In the day to day work of real world project management, it is important to have clarity about which of these concerns are negotiable in service to the others. The most common scenario we see in our work is that clients want to create the best project possible within established financial boundaries, and will therefore prioritize some balance of quality and cost over time. While the schedule will be important, they will accept a timeline that does not unduly stress quality or cost outcomes. But each project is a unique situation and needs to be managed accordingly.