I'm not so sure about that; I personally consider policies coming with Innovative to be really great. Aristocracy, on the other hand, is just meh in this regard, while being quite good if measured separately.
Runaway human nations in SP do not need 20% infantry combat or any such, and by the time you're seriously considering using policies, a SP nation is usually talking FL potential over 100 (or much more if you have a good start). Aristocracy's SP draw is that it hands you a diplomat, an extra general for split fronts, and lets you easily NF off military and keep up. That it gives your generals a +1 shock boost is a useful extra as well, but SP is the kind of thing where basic bait tactics and stack comp will carry any blobbed nation without issue, and where after the early game you can fearlessly run DotF for -WE and a little extra power.
If you happen to go republic it lets you get a good +RT policy along with diplomatic too, but that's more situational.
*shrug* I feel the first group is too early for a military idea, because you'd rather be ahead of time in tech. But depends on a million things and clearly people here have very different ideas of what to do as France. Personally I went with influence first in my only 1.8 France game so far.
Despite our discussion here, in SP I'd pick influence first also.
Percentages are the only way you can really put it into practice without assumptions, but sure. For you to get 10/month from economic you'd need ~300 BT (giving roughly a 50/month base of tax income + production) and a 50/month army. You have these if you have the whole French region most of Iberia, for example. Among other things that means you no longer care about money because of all the trade income you are making.
Is economic really THAT weak? I feel like it's stronger, but maybe that's due to its -cost on buildings too. As I said though, knife to the eye either way

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Economic is actually solid for nations like Mali, Songhai, and Aztec. Inflation takes a heavy toll on ADM for those nations (that or you walk into financial ruin idiocy event lol); at that point it's fronting a substantial ADM savings on top of the normal money benefits, and these regions of the world get good manufactories (trade companies and plantations) relatively early while not having the same kind of income as France by default. I would find it really hard to justify picking economic for anybody else, unless as someone else you quickly wander into the Mali region and snap up huge gold income early on.