IRON TRIANGLE

It’s called the Iron Triangle, also the project management triangle, the triple constraint and the project triangle:

“You can have something done fast, cheap, or well, 

but you can only pick two."

Here is a visual depiction:

Comments:

The saying refers to the trade-off between speed, cost, and quality.

The idea is that you can't have everything, and that if you want something to be done quickly and cheaply, it will be of poor quality.

Some examples of the trade-off between speed, cost, and quality:

Good and fast: Expensive

Fast and cheap: Poor quality

Good and cheap: Slow

However, this trade-off doesn't always apply:

• Usability: In usability, the fastest and cheapest methods can sometimes be the best.

• Secondary service: A business can offer a secondary service that's faster and cheaper than its main service. This allows the business to deliver an acceptable "lower quality" to a customer.

• Do it yourself: A person can spend their own time learning and refining a skill to eventually reach a "good" outcome with little money spent on external services. However, this is often the exception, not the norm.

Also:

In practice trading between constraints is not always possible:

• Throwing money (and people) at a fully staffed project can slow it down.

• In poorly run projects it is often impossible to improve budget, schedule or scope without adversely affecting quality.

The origins are unclear but it has been used since at least the 1950s.

It is also sometimes expressed as ‘You get what you pay for.”