Every year in a software development branch of IT business, significant amount of money is spent on quality. Why is quality so expensive? Is quality so important? Why do companies spend money on Quality Assurance and Software Testing Departments maintenance?

When I think of it I come to conclusion that software quality verification sometimes is even more expensive than software development itself.

Sometimes the quality of software means everything. There are a lot of examples of such systems: the software for railway and air transportation, banking and financial software, healthcare. If something is done wrong in this kind of systems, and if it is not found and corrected on time, it may lead to serious problems in healthcare, or even result in numerous casualties. Often a number of testers taking part in project implementation is more than a number of developers. But every found bug will eventually save money or a company’s reputation.

I took part in this kind of projects. The team had been working on software for medicine distribution for 2 years. There were 9 people who tested the project and only 4 programmers. The price of drugs was rather high, thus a testing team spent much time carrying out their tests with precise care in order to find all the defects that could affect the system. The main requirement for such systems is high accuracy of calculations. And testing engineers repeat the same actions again and again to make sure that everything is correctly calculated. If system had a bug, patient would have received an overdose and possibly died.

And how many do you prefer to pay for quality?

rhetorical question?

Aet

Actually we are realy interesting in this problem.
As it sems all customers search for the best ratio of quality and price.

OP: You answered your own question in your text.

Quality is expensive because it takes time... skill... and a willingness to be so damn thorough you want to claw your eyes out.

Writing code is one thing but layers of add ons, patches, fixes, redesigns, and interaction produce complexity that needs to be checked. Rare is the program that is expensive and some how straight forward.

modi123_1, thank you for your opinion!
It is so. But some people are surprised by the high prices and prefer cheaper product even if it is low-grade.

I guess.. but people who accept low grade work are not working in mission critical systems... like your example - with medical tech. They can accept the collateral damage then that's the buyer's prerogative.

Thanks! And do you work in mission critical system?

Yup.

It's commonly said that software can be written fast, good and cheap: Pick two. I've found this to be true.

Oh! I suspect you have an interesting and useful experience! Can you tell about it some more?

I'm reading Code Complete 2 and maybe you'll find this information interesting. Studies said that formal code review (like pair programing; self code review, etc) helps to find a lot more defects than unit test, continuous integration or testing . To achieve software quality it's important to set some quality rules to reach (robustness, correctness, efficiency, readability of code, etc ) and among them which ones developers have to focus more.
And not just believe that you can do quick and dirty code, and fix the bugs with a big testing team.

Well it's in the book but it makes sense to me. System are big and complex, it's really hard for a human to test everything, it's better to try to detect defect the earlier possible.

This is a classical engineering problem commonly referred to as the "quality triangle" ("good, cheap, fast" as mentioned by previous poster). It's more complex than that, but that's the basic idea.
http://en.wikipedia.org/wiki/Project_triangle