Agree with Rackend. Most of the providers these days offer lower level DDoS Protection for free. For Example: all our Bulgaria Servers have upto Layer 7 DDoS Protection whether you ask for it or not, its free.
But as Rackend said DDoS Attacks these days are very heavy. A routine level DDoS protected server can defend against low level DDoS Attack easily, but when there is a bigger one, then you can't do anything. In case you want to fight those big attacks then those DDoS Protected server are real expensive.
Pricing difference is huge depending on the level of protection, server specs and location.