I dislike the argument of "its cost efficient". Just because somethings cost efficient doesn't necessarily make it a good item on half the things people build it on. Its like saying because IE is cost efficient i should build it on ryze as well (ok not really but you get the point maybe). Frequently I see people build RoA on shit like Lissandra, Annie (This one i'm almost 50/50 on too just because I've done it a few times but never quite liked it), Brand, Morgana, Diana, Malzahar, Syndra (kill me). It just sucks that they're wasting so much damage potential from those champions on an item like RoA.
a lot of mids in plat seem to think roa is a substitute for athenes...its not and grail is still good it was fucking op before the nerfs now its still a good item! or they build fucking morellonomicon on ziggs and cry that theyre always oom before fights. fuck plat in general
RoA is a fine item for mana fixing, what makes it not-a-substitute for Grail is that it doesn't have CDR. Morellonomicon doesn't have enough mana regen on it, only works if you're playing a champ that is just on the edge of needing a tiny little bit of mana help, or you
really want that grievous wounds passive.
Almost everything is "cost-efficient" but you have to look at the stats you're getting and the champion you're buying it on. I don't mind RoA on all but a few AP champs because hey, Health and AP are two stats that are universally good. And not that you should but even ignoring the mana it's cost-efficient at full charge, just to showcase
how insanely efficient it is. Plus Catalyst is still the best rush item in the game for a strong laning phase short of maybe triple Doran's Ring.
Honestly, the only reason I've mostly moved away from building RoA is that Grail's CDR is all too necessary by lategame and that obviates the need of other mana items. At that point I can just get HP from Rylai's and/or Liandry's instead and now RoA is redundant. Of course, you could also get RoA and pick up CDR from somewhere else but unless you need Morello's passive, the only other sources are 10% from DFG or Twin Shadows. :[ Archangel's getting that Seraph's upgrade at the start of S3 further marginalizes RoA, since with the active ability it's almost like a more offensive RoA... and nobody appreciates survivability anymore. :(