[Ygorl]

OK, "ludicrous" maybe implies more of a judgment than I meant to make. How about "pretty much the biggest possible games"? Anyway, are those late-large-game ANs cast for 150 pearls, or are they buffed? The few times I've actually seen AN cast (all back in Dom2) it was either cast at really high strength, or else cast at low strength and allowed to survive for several turns and then recast at really high strength. One game turned into a big AN war, with me and one other player allied against the third (dominant) player - we eventually managed to dispel his 999-gem AN and put up one of our own in the same turn (at a cost of about 1900 pearls). I think the three of us maybe decided at that point that the game was silly, though, as the other guy had basically won anyway. The other game, AN was put up by Pythium; he kept it for a while, then it was taken by Ermor. Pythium tried to take it back with 700-some gems (all he had saved) but failed - Ermor had used more to cast it, thanks to massive clamhoarding. Pythium was in a fairly strong position, but it would have been shocking to see them win; Ermor was one of the strongest players, especially after many turns with the Nexus up, but was probably not the strongest player and in fact was suffering some pretty serious losses when we called the game on account of Dom3.
I vaguely remember seeing it in one other game, but if so, I don't think it changed the course of the game in a significant way.

For the Nexus to be pulling in 250 gems per turn, wouldn't that mean that people were spending 1000 non-astral gems per turn? Isn't that an awful lot? Like, the entire gem income from a fully-site-searched 300-province map? People don't restrict their spending when the Nexus goes up? I don't know. My experience obviously is limited, but it's always seemed to me to be a spell that either confirms something that everyone knew anyway or else a spell that is viciously fought over, draining lots of resources from everyone involved in the fighting, with benefits (considering that resource drain) not out of line for its cost and research and path requirements.
Also, keep in mind that anyone can dispel a global, simply by casting another one with more buff-gems and getting lucky on a 1/5 chance. I don't generally think this is a good idea, as spending hundreds of gems on a 1/5 chance when your enemy has the Nexus up seems kind of counterproductive, but if you get truly desperate it could work. It would still probably make more sense to spend those hundreds of gems blasting the holy hell out of the caster of the Nexus...

Anyway, that's one small man's opinion. Cheers!