Depends on the condition and completeness of each game.

A complete in box EarthBound usually sells for $250-$300. A stray EB cart averages about $70-100.
A complete in box MOTHER usually isn't too expensive, they go on YAJ for the equivalent of about $20-30 last I checked. Though I'm very unsure about this. I remember I got mine for 1600 yen, so that was about $20 at the time.
A complete in box MOTHER2 is about the same as MOTHER, so around $20-$30.
MOTHER3 complete in box sells in the $30-40 range.

So the whole Japanese set is worth about $70 to $100. So if you are trading just an EB cart, then you're getting a pretty fair trade, money-wise. If your EB is a complete in box set, no way.

But consider personal value as well. If you only have one EB cart and don't know Japanese/don't have the Japanese systems to play the MOTHER games, then that might be enough reason not to trade.

I've been thinking about this a lot lately as I've reduced my collection of other series merch to one piece per game and sorted through to the stuff I really want to keep. In the pantheon of actually obtainable merchandise I'd have to go with the Mother 3 handbill. There were several handbills produced over the series' lifetime. You can see very small thumbnails of them here. There are five in total and I've managed to track down the common red Mother 2 Flyer and the semi-rare to rare Mother 1 Flyer. I would really, truly like to have that Mother 3 Flyer but it just doesn't want to surface or...maybe I don't know where to look.

The only lead I've had so far is this posting on E-102 Gamma's fantography section over at Starmen.net. I found this just while browsing around sm.net and my eyes almost fell out of my head. Unfortunately I have no way of contacting him and even if I could get ahold of him I highly doubt he would let go of it. I really would like to 'complete the trio' up on my wall but I just can't seem to find one of these anywhere. Does anyone have any leads besides the usual YAJ/Mbok pair? Does anyone have one for sale? Any help on this would be hugely appreciated but I just seem to be striking out left to right as handbill collecting is super-niche as it is.

The only other piece I would really like to have is the M1+2 Poster that was used at the launch event. She's an absolute beauty, that's for sure.

I've had at least one of all the different plushies and the keychains over the years but I've ended up letting them all go for one reason or another. I'm hyped like crazy for the upcoming wave of figures buuuuut there's a little voice in the back of my head saying that I might just be wasting my money again. It's the artwork that really jumps out at me and drives me bonkers.

Onion, you and I need to talk MOTHER merch.

That blue MOTHER 2 handbill is..... perfect. That is what I want.

Good luck and godspeed. That particular handbill is rarity manifest wrapped inside of scarcity. I can't even find a photo of it to confirm it exists besides that blurred out thumbnail.

I've officially changed my answer from whatever I posted earlier to the EarthBound poster.

Seeing that I don't have any merch that relates the EB or Mother, I would say: a Earthbound poster, or a Mr. Saturn plush, or an untouched unopened copy of Earthbound.

From the game I'd Probably Ask for:
- an absolutely safe capsule
- a cracked bat

From Fangamer:
- a Courage badge keychain/keyfob.

I think a few posters would go nice in my room, Besides that, I would want a proto,