My impression currently is that economy is about right, but that the relatively recent change from paying for almost all energy to not paying for much or any energy is skewing the views of long term players. Someone mentioned the cost of operating all those energy reactors that we used to have to build, and having had to pay resources to operate them really was a significant drain on the player's economy, even if it wasn't usually noticed, and when the price paid for energy disappeared, in combination with the buffs to harvesters, people who had been playing for a long time suddenly saw an enormous increase in their resource income. You were spending 67 metal and 67 crystal (134 total) for 125 energy per system (assuming one of each reactor in every system) prior to 5.040, and gaining 80/120/220 resources (both types summed together) per planet, assuming that the current harvester income numbers are valid at least back to 5.033, which meant that a set of energy reactors caused an average planet to be a net drain on your economy with Mark I (-57 resources/s) or Mark II (-17 resources/s) harvesters, and a modest boost to your economy with Mark III harvesters (+86 resources/s), not counting any income or cost from the command station.
The player base is probably still used to having an economy somewhat like what I described above, and so with the disappearance of the energy reactor and the addition of the energy collector, we feel as though we are swimming in resources when we're playing in a similar manner to the way we had played for years prior to these changes. Just looking at the above, it's like I'm starting games with the resource income that I'd end games with under the old system, and any harvester upgrades I unlock greatly boost that. Moreover, in the old system you would often run into situations where either metal or crystal was in particularly short supply, since resource nodes are not necessarily evenly distributed but the resource costs of energy reactors were evenly split, which meant that you'd often run out of one resource long before you ran out of the other, and activating the manufactories to allow you to use your remaining stockpile of whatever resource you had more of meant that you'd run down your resources even more quickly than you were doing so before (which is still the case, and even if nothing else remains the same, this should be unchanged).
For that matter, before upgrades of harvesters were introduced, your economy was entirely reliant on what are now the Mark I harvesters, which means that players who have been playing since before harvester upgrades were introduced learned to play and began forming their preferred strategies on economies far weaker than what we have now, and that period when they were learning how to play probably has a reflection in some of the comments on how strong the player economy now is. I know that a lot of the impressions I have of the AI War player economy come from comparisons with the economy that I remember from when I first started playing AI War, and, despite the changes in the player economy, the things I learned about the game economy at that point in time still have some degree of influence over the unlock choices I make from the start of the game. I'm a bit doubtful that economic upgrades would be quite as popular as they seem to be currently (based on forum posts) if everyone on the forum were just starting to play the game, because many of the older players are used to a weak economy, which at its strongest was similar to what the current economy is at its weakest (until you start throwing in energy reactors, but I have only rarely needed energy reactors, and that's usually only if I am not taking many planets, or I've built up a large starship fleet), and so jump at the chance to improve it, and as a result we get situations where people are swimming in resources because the playstyle that they developed pre-harvester upgrades or especially pre-energy collector to conserve their forces and allow their economies breathing room between having to rebuild the fleet or work on major construction projects.
That's not to say that there are some situations where the current economy gets excessive, but a part of that is from the champions, and a part of that is from having other things active at the same time. As an example of excessive economy, in my current game, I have a total income of 4028 metal and 4728 crystal (currently at about 1800 and 2400 due to some expenses - I might be building a radar jammer II on one of my worlds) with about 130000 spare energy (full caps of six Mark I fleet ships, Scouts I and II, and all Mark I starships, plus however many spire ships six shipyards supports, and the stuff from the nebulae), and I have ten worlds (and four nebulas - Gray Spire, Mourner, EER with an extra IMT facility from before the glitch that caused extras of those to spawn on load was fixed, and Shattered Pillar) and three spire cities (two habitation modules per city, not that it's necessary), and a total of 17 metal and 24 crystal harvesters, with all six Mark III economic stations built and one Mark II economic command station, with Mark III harvesters on each. This, naturally, is a completely excessive economy and is capable of funding just about anything I currently can do (including, at one point, simultaneously building three Mark I ion cannons, a Spire City, and funding repairs and ship replacements while holding off an exo-wave) without the risk of the economy going under. This particular game was started perhaps in 5.9 or so, though I'm not really sure. It's an example of the extremes you can reach if you focus on economic upgrades and get relatively average resource points on your planets, and I rather suspect that many of the players complaining about the strength of the economy do something like this.
First thing to note about that, though, is that I'm getting 1800 metal and 1800 crystal from my Spire Cities alone, which means that without Fallen Spire my income would be about half what it is currently. I'm also getting the resources from five nebula facilities and a Rebel Human Colony, which together represent another several hundred of each resource. So, an equivalent game with no extra AI plots or minor factions or champions on would have me sitting at about 2000 metal/s and 2600 crystal/s, which is less excessive of an economy and still represents 18000 knowledge spent on the economy, out of the about 40,000 knowledge I have access to off of ten planets, which could probably have been better spent, but I'm planning on taking over most of the galaxy anyways - what else is Fallen Spire for?