Fresh blood vs old hands concept in IT companies

if we want to get good salary package in IT company the only way is to switch the companies every 1 or 2 years this is the mantra that is going on in IT for a long time, this is because managers are willing to pay more for a new experienced person from outside the company than the same amount of experienced person inside the company... it looks like the managements are following a hiring strategy what is know as "fresh blood vs old hands" concept that says a new person with same experience can contribute more than the person with same level of experience already in the company though this might not be true in all cases.

I was for long being in the conception that working for longer period of time would look good in the resume and also its a kind of loyalty to pay back to the company but some times i feel i making a mistake and still left puzzled as i can see some of my colleagues and friends who hopped more than twice with the same experience as mine is getting twice the pay...

and recently i understood no matter how hard we work we will not get a decent raise until we switch the company a mantra which becomes a must for ever IT professional though i am still puzzled some times i strongly feel it is imminent let see how it goes :) and one question remains does switching jobs frequently is only way to get paid more?