ACtually it is a good deal. In technology your skill set can advance much faster than your promotion prospects at one company and when you can get a 40% raise by jumping, it is worth it.
In traditional engineering disciplines, you cannot get a 40% raise by jumping companies. That kind of jump may be possible for some of the boom and bust fields if you catch the boom cycles just right, but it's not going to happen for most of us who are taking care of the business of making the things that society needs.
That kind of jump also depends on being a smooth talker and negotiator. Who is going to value you more, those who have seen your performance and worked with you over time, or those to whom you try to sell yourself as the greatest thing since sliced bread? That's a basic difference in personalities. Some people are good at hyping themselves. They can sit down with someone and paint a picture, and that picture will always be better than the real thing. Others are the opposite. We sit down and talk to someone, and we don't seem so impressive. However, those who've worked with us over time realize that we are solid performers who are worth much more than the "knights of spin and hype." Unfortunately, they can't tell from those first conversations whether we're really that good or whether we're as middling as we seem.
Bill