I thought I had posted this before, but maybe I didn't hit submit... Step 1: RP2-IC2 Watermill Systems. Step 2: ??? Step 3: Profit.
Sounds good to me, not sure on the price yet, diamond block/2 chunks maybe, I dunno. I am also concerned with the only above a certain y coord as my base is literally built at bedrock to level 30. Don't go hating, and saying I should've built above ground, I did it for the challenge. Other than that, I'd say this is a good idea.
I was thinking more like a stack of diamonds per chunk. With your plan I could buy more than 8 chunks/day. Also, watermill systems should be banned.
I would say that they are the primary cause of this kind of problem, especially considering they are cheap, easy and I can guarantee at least half of the players on this server would use one. With our reasonably large playerbase, all those timers add up, especially when loaded with ChunkLoaders.
Maybe sk could set up a trade station so that people could exchange watermills for their components making people less likely to rage at their banning? Also, we should encourage people to use timer-less systems where possible (e.g. RP2 Relays). I've been converting a few of my pre-PR5 systems to use relays instead of chest -> filter (with timer). Worried about relays ejecting everything where you only want to eject certain things? Connect a filter inline to the pneumatic tube line to prevent unwanted items from being ejected. Relays are smart enough to only eject stuff that has a valid path/inventory. I'm sure if everyone helped out like this, sk wouldn't need to take such drastic measures in this matter (except banning watermill lag machines - those need to go).
Timers don't use much CPU. It's what they trigger. Relays would induce destination checks, so that wouldn't probably be any better. That said, I do not advise anyone to need to worry about this stuff. Just build normally.