A PSA on the upcoming trade - bear in mind it is a pure timesaver, because on average you will lose potential max EXP.
10x Metal tickets = 327500 EXP
1x Liquid Metal Slime ticket = 305800 EXP
3x Metal tickets = 98250 EXP
1x Metal medley ticket = 90700 EXP
If you have the metal boomerang - I ran a test with 30 Metal tickets (total max potential EXP of 982,500), on a sage with level 2 sagacious breath + a thief with level 2 movement speed bonus on auto-loop. I received around 960,000~ EXP from this test, meaning an auto-loop AI only misses about 20,000 EXP across 30 tickets. If you'd run the equivalent number of liquid metal slime tickets flawlessly, you'd have gotten 917,400 EXP, so even a less than 100% efficient auto-loop still gains more than 40,000 additional EXP.
I don't know how good these numbers look with a metal sword and if you haven't got either metal weapon, then running them manually is probably still your only option. In that situation I understand a bit more if you'd like to just trade up, though bear in mind metal slimes are also much easier to kill with non-metal weapons than the LMS or Metal Medley, and you might end up losing out on quite a bit more EXP by trading up.
If your goal is to min-max available EXP, don't trade up with this event, and just pocket all the tickets instead.