Is it worth it to do item hunter now? I last tried it a few years ago and gave up on it because it was eating my sp.

The first 5 quests often eat sP, but not too much, we're talking a couple of thousand at most. Then 6-40ish are usually profitable. From 40 on its a crap shoot, might be very profitable might not. The big benefit as far as I'm concerned is that you know exactly what you're going to make and can decide to quit and restart at any time. Once he asks for a Subeautique item, that's when I usually quit (unless the item actually happens to be in the shop at the time).

The big thing is deciding when to quit ahead of time. I'm cheap, so past level 5, I'll quit when/if he asks for an item that costs more than twice what the reward will be. When that happens, its not usually possible to recoup your costs in further quests - because they usually just get more expensive from then on.

That's my issue--I don't know what he usually asks for past 50, so I'm wondering if overall it at least evens out.

No it never evens out. Once you start getting expensive stuff, it just gets worse. Sure sometimes you run into stuff that still makes a profit, but not enough of one to continue. That's why I stop when I start getting requests for items that cost 2Xmore than the expected reward.

Unless I want to activate Chase or actively work on those higher level achievements. Then I decide how many millions I want to spend doing that.

Good to know--I'll skip it then.