Like the other secondary stats, the question you ask implies that it's a linear relation (but it isn't). E.g. look at skill speed. Let's say (it's pretty accurate in this example) that 10 point of skill speed decreases AA delay and GCD by .01. Then by adding 100, we've only decrease to 2.4, which is 2.5/2.4=4% increase. Adding another 100 on top of that decreases it to 2.3, BUT this doesn't increase dps by 4% (like the first 100) the new dps increase is 2.5/2.3=8.7%. And while will doubled stat investment, we've more than double the change to dps. So in other words, when dealing with secondary stats you can't assume a linear formula.