There are other tradeoffs - for the most part, faster strings are made lighter, so they travel quicker. This is accomplished by making shorter servings and/or using smaller diameter serving material. They also often use fewer strands of string material, which makes the string lighter. There are some string materials that are naturally a bit faster. However, they stretch more - something I don't like. You end of with a string that is faster, noisier, weaker and more prone to movement (creep, stretch). In essense, it's like shooting a lighter arrow, so it's harder on your bow (read more vibration), so the bow wears out sooner. On any given bow set-up, increasing speed will usually come at a cost. Often times, the price is much higher than any benefit from a bit more speed