I've been working through some of the maths for possible tech costs / KM effects...
105 total
techs in the game.
New tech cost by tier (1, 2, … 7): 40, 60, 120, 360, 1440, 7200, 43200
Base Knowledge Maintenance (KM) is +0.1% increased tech costs
per tech known
per population point in your civ.
Keep in mind that the goal here isn't to finish the tech tree. You should be going for some victory condition with anywhere from 15 to 50 techs, depending. (If
you aren't, an AI will.) That may or may not include one or two Tier 6 techs. In most games, probably no one learns a Tier 7 tech.
Your first city usually gets to population 2 in a few turns. A pop 2 city makes 5s/turn (2 from pop; 3 for capital). That gets you a tier 1 tech in 8 turns or a tier 2 in 12 turns. So that gives you an idea for civ naming -- anywhere from 12 turns to twenty-something, depending on how you do it. Policies will be calibrated to be similar in pacing, so not more or less likely to trigger a civ naming.
Let's call a "low tech" civ one that makes 1s / pop, and a "high tech" civ one that makes 5s / pop, regardless of total population. Of course, it will be quicker to get a small civ to 5s / pop than a large civ.
A
tiny high-tech civ benefits from low KM (from pop) but suffers from low
total science per turn. If you had 10 total pop producing 50 s/turn, that would allow you to research tier 5/6/7 techs in 29/144/864 turns, respectively. KM is pretty mild here, since you would have to have 50 techs before you see a 50% increase in tech costs. Yeah, I know the turn counts kind of suck, but you're really turtling at 10 total population.
A
mid-sized high-tech civ will see KM kick in a little harder and earlier. Let's say 50 total pop (5 cities at size 10, 10 cities at size 5, or whatever) producing 250 s/turn. That gets you to tier 5/6/7 techs in 6/29/173 turns, respectively, without considering KM. KM is steeper here, with +100% tech costs (double) at 20 known techs and +200% tech costs (triple) at 40 techs. So the turn counts above become 12/58/346 and 18/87/519, respectively.
A
huge high-tech civ could have population 250 (say 8 cities at size 30 or many smaller ones). KM is a real factor here but you're putting out massive science points: 1250 s/turn. Without KM, that's tier 5/6/7 tech in 2/6/35 turns. But now we have +500% tech costs at 20 known techs and +1000% tech costs at 40 techs. So the turn counts above become 7/35/207 or 13/63/381, respectively.
You can do the math for a "low tech" civ in your head: just multiply turn times above by 5. As a big low-tech civ, you can still eat up low tier techs pretty quickly. You can reasonably get a tier 6 tech (e.g., Mumakil Riding) if you beeline for it early, before getting too many other techs (in this case it's possible with only 9 techs known). Or you can spread out and pick up 20-30 low to mid tier techs, which probably will cover all your needs for resource development plus some good (but not fantastic) military units. Either approach will work.
It looks like HUGE wins in the analysis above for high-tech, despite the added KM burden. To some extent, that's true and I'm OK with bigger-is-better in this area. But notice that 5x bigger is not even 2x better in comparing huge to mid-sized. And there are other factors, like time needed to develop cities, big civilizations making more enemies, and the fact that big civs will have to spread out in the tech tree more to develop more different resources. I suspect that a strong early research focus in a few cities will be the fastest way to get into the higher tier techs, if that is your goal.
346 turns to get to a Tier 7 tech?!!! Let me answer this a couple ways: First, these are at the top of four branches that are going to have a lot of very specialized research boosts (e.g., Arcane Towers and Thaumaturges contributing to research and/or lowering costs for arcane techs). So that number is probably off by a factor of 2 or 3 if you are really focused in one of these areas. Second, these are all game-ending techs. If a civ reaches one (either you or an AI), the game is probably going to wrap up in short order.
Is there KM deduction for techs along the Writing branch (Philosophy, Logic, etc.)? Not planned for now. What you have in this branch are buildings, Tomes and other things that you will need if you hope to reach 5 s / population point, and maybe even higher research rates with the top one or two techs in this branch.