Originally posted by shawng1
Castellon,
AHH, I'm not a math major. So you'll have to take a very crude example.
Which may explain why you miss (or deliberately leave out) something from your calculation
There are significant benefits to gaining medium tech levels in both trade and infrastructure quickly, rather than focusing on one area. The most obvious, as you mention, is trade 3 (for monopolies), but trade 4 (emargoes) also comes to mind. (One of the higher trade levels also adds an extra merchant, but I forget which).
However, infrastructure does give you the tax collector, FAA, refinery, judge, governor, and goods manufactory upgrades.
By climbing the trade tree first, you pay extra for every aspect of the game (recruitment, upkeep, building &etc) since you don't have your inflation under control. While this works well for rich nations that seldom (if ever) need to coin money, it doesn't work well in general.
And it ignores the fact that infrastructure levels above 5 give at 10% boost while trade levels above 5 give a 5% boost.
And the detail, that the way the manufactories currently work it pays better off in terms of research and income to build refineries and goods manufactories - at least for the first score or two - assuming that 1) You have the provinces for it and 2) You have control of your inflation - which requires higher infrastructure to build in the first place.
For a European nation a trade2, infra2, trade3, infra5, trade4 (if you need to monopolise), infra6, manufactories makes excellent economic sense.
However, I think your so-called crude example, is an excellent way to gain lots of money as a few-to-medium-province trading empire, since your merchants will be virtually indestructible and tech costs low, but for nations with a significant production income (or with a lot of provinces and a wish to abuse the manufactory system

- the 25% trade bonus for gaining trade6-10 is the same as the one you get for building 25 refineries with regards to income and merchant longevity, but also gives you research to gain the tech levels while you invest in something else) I don't think it is ideal.