So, survey vs discipline - here's why I'm not a fan of survey:
1. It forces you to open Scout first. Now some people might do that blindly every game and do fine with it, but I much prefer to have the flexibility to open up with other things as well, because sometimes there are more optimal (imo) choices depending on the map layout. In my preferred order, I usually open up with Slinger, with a warrior on second place and builder/scout on third place. The reason for this is that because I play on Deity to Deity++, slinger is just a much safer option. It gets my military score up higher, making it less likely that I get declared war upon in th early Ancient era. It also allows me to get an early Archery eureka, which is usually an important tech early on for defensive or offensive purposes. And since I already have a Slinger built, it upgrades nice and cheap into a "free" Archer that I can either defend or attack an AI with. The Warrior is an even safer opener, as it gets my military score up even higher, and allows for a second unit to roam around clearing camps, while being a strong defensive unit against an aggressive AI. The builder/scout is my third option, and is essentially my "greedy option" for when the immediate layout makes me feel somewhat safe. Typically if I have coastline near my settler (especially so if tundra) because it means I can generally only have neighbours in one or two directions, making it much easier to know where any threat will be coming from. This still depends on me having hills and woods around my capital, because a capital situated on complete flatfland on all sides is gonna get steamrolled by an AI if they decide to attack me, no questions asked. In this case though, a builder is the most greedy option (but can set up a nice early snowball), whereas the Scout is somewhat greedy as well (because it has limited value in terms of military score, and is a gamble on whether it pays off enough compared to the guaranteed payoffs from a builder). Typically a warrior or slinger start allows these units to be used as limited scouts as well, so there is even less of a reason to pick a Scout if you just need to look for decent settling spots and know your closest neighbours. Either way, in any case where I don't open scout first (the majority of my games), survey is essentially worthless by definition.
2. It can make it harder to get era score, not easier. On the highest difficulty settings, it is a gamble on whether or not you get enough era score payoff from a Scout to make him worth the investment. Whether or not a scout is worth it in terms of era score depends primarily on the number of tribal villages you can pick up, which are usually quite scarce on Deity or above because the AI tends to scoop them fast. You can also get some era score from meeting neighbours and finding a lucky natural wonder, but since you can use a Slinger or Warrior to scout a bit with as well, the marginal value drops on the Scout. Meanwhile, another warrior or slinger will let you clear barbarian camps much faster. Not only because you didn't build a scout, but because you have discpline together with your extra slinger or warrior. And since barbarian camps are a very consistent source of early era score and gold, this opener (slinger/warrior with discipline) lets you get those sources fast, while also doubling down on a safer start against potential surprise wars from an AI (because your military score is higher). Now you will usually get a bit more era score from a Scout if he meets more neighbours and/or spots a natural wonder, but this comes at the cost of being much more vulnerable and much less able to clear barbarian camps for era score and gold. The main reason people use Discipline is maybe "to defend against barbs" for players on lower difficulty settings, but on Deity and above most players know how to defend against barbs indirectly without extra combat strength. In this case, the extra combat strength from discipline is to clear barbarian camps faster and more consistently for extra era score and gold.
3. Survey adds very little value in itself for era score, as is your main argument. You can still open up with a scout while running discpline, the only drawback here is that your most important promotion (the first terrain one) is a few turns later. That's it, that is essentially all you gain from Survey, getting the terrain bonus a little earlier. On the flip side, any stray barbarians are that much more likely to kill or cripple your scout, so that it's really up in the air on whether even Survey is worth it over just Discipline, even if you open scout first.
The rest of that napkin math of yours (where you essentially try to draw a direct causal link between time spent on a scout into raw gold cost on saved builders from monumentality in the next era) is so dubious that I'm not going to answer that further.