I didn't bother looking at your Wiki-link for "perfect competition" because it sounds like socialist gobbledygook. There is no such thing as "perfect" anything, and if you live your life dreaming of perfection, you will end up very disappointed. There is healthy competition in a free market capitalist system, and this is what drives it.
To illustrate how competition forces work, let's take the example of recently declining gas prices. Where I live, gas has now dropped to $1.91 a gallon. Now.... I have to wonder... why aren't all those greedy rich Big Oil types charging me $3 a gallon instead of $1.91? I mean, we know they are greedy rich bastards who want to make every dime they can because of all the record profits, so why are they short-selling the product? They'd have most of us kissing their butts for $3 gas.... they're missing out on a huge capitalist opportunity, right?
But that's where good old competition comes in. A lot of oil on the market right now means low oil prices, so the price of gas goes down as a result. Wholesalers competing with each other sell their gas to dealers at lower and lower prices, dealers reduce prices lower and lower to draw new customers. It's a remarkable example to show how free market capitalism works and continues to be the best economic system ever devised by mankind
The concept "perfect competition" is economics 101, not a socialist gobbledygook.
For capitalism to work as you described perfect competition is a requisite, else, market bubbles and market failures start to appear, this is the part where regulations have to be enacted.
I'll give you a counter-example : healthcare. USA has the most expensive healthcare in the world, and believe me it is not the best. Most of the reason this happens is because of the interaction between insurance companies and hospitals
"Between 2000 and 2006, wages in the United States increased by 3.8%, but health care premiums increased by 87%."
18 Ridiculous Statistics About The Health Care Industry That Will Make Tear Your Hair Out - Business Insider
This is what is called market failure: supply and demand are no longer able to yield fair prices. This is a delicate situation specially in healthcare, because demand tends to be quite inelastic.
Market failure - Wikipedia the free encyclopedia
Same goes for microsofts overpriced products , a company with a monopoly can clearly set the prices, put a bad product into the market ( e.g. windows vista ) and force the consumer to upgrade.