10% first step at 4 is probably about right.
My point is that getting a bonus of acceleration equivalent to +10 speed/agility (what you call 40 skill points) is wildly inaccurate.
Even if the equivalence to 10 speed/agility was accurate, despite being a random guess...
let's weigh the options..
4 First Step - "equivalent" to 10 speed/agility
-only during the acceleration
-only on some low % of snaps
Straight up 10 speed/agility
-gets you the exact same acceleration as the 4 first step would
-you get the speed/agility on every snap
-you also get the speed/agility for movements OTHER than acceleration, such as moving in the pocket or moving once you're at full speed on a pull.
With that in mind, even if 4 first step was somehow worth 10 speed/agility, which if you valued at 40 skill points opportunity cost, that 4 first step absolutely plummets in value when you consider the circumstances you are USING that 10 speed/agility. Nowhere near 40 skill points in value, if I had to guess.
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I stand firm that using 64 bonus tokens (16 skill point opportunity cost) is absolutely not worth going from 0 to 4 in First Step.
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A very easy decision rule, though subjective, is to simply answer the question: Would you spend 16 skill points on 4 first step, if given the choice. I don't care about this whole "how do you value something you can't buy".. YOU CAN BUY IT, it is in the shop. I have a feeling most people would say "no" even without doing a further analysis to try to figure out what first step is actually doing in the sim code.
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Including +3 agility is a nice thought, however. Ask yourself the question though, how much is that 3 agility worth? If your answer is 4:1 because you're in the 4:1 cap, you need to follow the decision rule again: Would you spend 4:1 on agility? You didn't did you? Or you'd be in the 5:1 cap. Therefor it ISN'T worth 4:1 each. I'd say that +3 agility is worth 9 skill points.
So now would you spend 7 skill points on 4 first step? Well, maybe
However, my answer is still no, because of the
existence of even more valuable advanced equipment opportunities. There is an implied cost in equipping this piece, namely you CAN'T use a BETTER piece because you chose this one!
The value is out there to find, and I just don't see it in a first step piece