Unless you pick up specific policies, you're often looking at something like 500 gold for 40 rep (or 1000 for 80, same ratio), meaning you're paying 12.5 gold per turn for 16 faith per turn. Not much better of a ratio than Shrines/Temples. And that's not counting having to get them to allied status in the first place.
No, it's not. Ultimately you need to pay money or production to ally with the CSes. It could be flat out bribes. It could be weaker trade routes to them with the Freedom tenet. It could be gifting produced/bought units with the Freedom tenet. It could be a massive army with the Autocracy tenet (though that's very difficult to do on Deity). Etc. I'm going to work a 2 food/4 gold tile over a 3 food tile. I'm going to bribe CSes over Research Agreements or rush buying Science buildings as necessary. In short, I'm going to sacrifice at least SOME Science in some manner. Everything is an opportunity cost (I trust you're aware of that concept) -- spending more effort on CSes has to come from SOMETHING else.
I don't have a lot of these issues with CS's some people apparently have. Are you not using spies to coup or something? Anything within 80 influence is a 75%+ chance to coup with a level 3 spy. I pay literally pennies on the dollar for influence, and that influence keeps on racking up.
Here's an example. Lets say Vatican City has a trade route quest, and is allied with someone else with 100 influence. Trade route gives me 40, spy is an 85% chance coup, I've got an ally, probably a lux, and 16 fpt for the cost of a few GPT sending them a trade route instead of a better one. Of course there's an opportunity cost there, but that opportunity cost is not 1k gold every 40 turns like some people would like to claim. It doesn't really matter what VC i'm going for, I have most of the world on my side on almost all games. Spies are a neverending supply of literally free influence. Someone pays money to take Vatican City back from me, I coup them again and I'm EVEN MORE influence up. What else are you doing with spies midgame? Level a spy up to 3 via your own capital or someone elses, then send them off to CS's. It's so trivial as to be borderline broken. Sure, occasionally I have to throw down 1k gold and wait for an election rig in order to get a 200+ CS from Greece. That happens. But it's not anywhere near what the "cost" says it is (talking about gold gifts here, which is what you appear to be talking about).
The beauty of Civ is that many ways work. Lots of ways don't, but you don't need to agree with me on what you consider a diplo/culture game for us both to get good results. I personally find that high science is always the key to victory. Of course I don't work some half assed 3 food tile instead of a pasture. I don't even build 3 food farms after Civil Service (before fertilizer), so that's never even an option for me. But I also make sure all my science specialists are staffed immediately, and after I get Secularism, I staff as many other specialists as practical because that adds up in a hurry.
I guess if you want to take that as not being literal enough in this thread, that's fine. I figure if you've been browsing these boards for years you've got some basic concepts figured out like a science specialist is better than a trading post.