how taxing ICE is in relation to its cost, how scary it is, and how easy it is to get through, which I think together account for almost all of the attributes of ICE
I think this isn't possible to be put into a formula.
OK, more serious now. I understand what you're trying to do is a formula that takes a piece of ICE and values it to decide what is best. This may have some uses, but will definitely not lead to a single ranking.
The first problem is that, to make a single ranking, you need to assign some weights to "tax factor", "kill factor" and "end the run factor". And those are completely arbitrary. What ICE you want depends very much on what your corp deck wants to achieve. As an example, those are ICE compositions of two corp decks I currently play the most:
- Ice Wall x3, Wall of Static x3, Quandary x2, Enigma x2, Rototurret x2, Grim x2, Archer x3, Chimera x2 (19 in total),
- Wraparound x3, Eli 1.0 x3, Pop-up Window x3, RSVP x2, Tollbooth x2, Caduceus x3, Draco x2 (18 in total)
The first is for a rig destruction Weyland deck (running Power Shutdown, Corporate Troubleshooter and Aggressive Secretary), which does not care about "tax factor" at all (it gives bad publicity right and left) and only cares about "kill factor" as long as it is "kill the Corroder factor". On the other hand "end the run" factor is extremally important and 17/19 pieces of ICE have hard ETR, forcing breakers on the table so I can trash them. The other is completely different. It comes from a taxing NBN deck, running SanSan City Grid, Ash 2X3ZB9CY, mixed asset/operation economy and NAPD Contract. Here I don't care too much about the runner getting in, as long as he is too poor to do anything important in the server, so only 5/18 ice are hard ETR, and it's not their most important part. Moving ICE from one deck to another would clearly weaken it, no matter which direction. They simply need different things.
The other problem is that while the three factors you mentioned, while they're quite important, are not all. And those other things affect deckbuilding choices a lot. For example Wotan is weakened by the fact it's unique. Paper Wall is weakened by self-trashing when broken. Wraparound is a cheap barrier but also an Atman/Parasite hate card. Big ice in general needs stronger effect than it should have according to any formula because it's vulnerable to derezzing effects and mostly useless early game when no corp can afford rezzing it other than via various tricks (which make it even more vulnerable to being killed in one or another way). RSVP is another example that escapes from your 3 factors - it doesn't tax (in fact it prevents taxing), it doesn't stop, it's scary only in some exotic combos (e.g. Whirlpool into RSVP into Shinobi) - but it's definitely playable in right decks.
