With NetApp hardware, you can sometimes add expansion modules and upgrades that will expand the life of your system without the need for a full upgrade. Even when you do have to upgrade, the costs are quite low compared with many other companies. IBM, while they are a good company that offers a lot to customers, tends to cost more. Those who are on a tighter budget and who want to make their IT money go further will find that NetApp is the best option when it comes to cost efficiency.
Consider for a moment the expense of buying, or even renting, all new equipment. Couple that with the costs of learning how to use the equipment and the short-term productivity drop that it could cause, and it becomes easy to see why sticking with a known entity, NetApp, makes more sense in every aspect.