Well since Cobblemaniac already answered the previous question...
You don't really need to trade in an MLB event eido, even just 1 copy with 0 or some limit breaks will give u something.
Something like:
Event SSR eido = 150 orbs (add another 150 per limit break, MLB gives 750)
SSR gacha eido = 750 at LB0 (well im sure you wouldnt want to trade these in unless you're a super whale)
SR eidos = 150 at MLB, 120 at LB3 (why I keep my disaster eidos... though i dont MLB them since it costs 10k gems to do so)
and yes, 1 copy costs 600 orbs, and you need 5 copies for an MLB'ed one so that's 3000 orbs total
I mostly kept some duplicate SSR event eidos that I got from past raid events, and because of the recent gluttony reprint, I have an MLB'ed duplicate lilim gula to trade in which is already 750 points.... (and up to you if you wanna trade every single lilim you get, i would keep my first original MLB'ed copy though)
Once that raid eido exchange shop comes, I can probably get an MLB'ed jack o lantern already
The hard one to save for is the kaiser dragoons, since they cost 10k orbs.... and every dark main should get the dark kaiser dragoon because it will benefit them greatly even at LB0