FTL exists. Cheap matter transmutation exists. What would planets trade with each other other than FTL fuel?

FTL exists. Cheap matter transmutation exists. What would planets trade with each other other than FTL fuel?

Nothing but intellectual property as nobody has anything worth moving anymore.

Labor and artisan goods.

Even in Star Trek with replicators people liked to have traditionally made foodstuffs.

And even matter transmutation requires energy, which requires energy production, which requires labor at some point in that production, as well as maintenance, 'cheap' simply allows for a larger consumer base.

Entertainment and art.

By 'matter transmutation' do you mean nuclear transmutation, molecular assemblers, or both combined (Star Trek replicators?)

Why would you trade FTL fuel, if you can just transmute it?

Whores.

A dyson swarm + army of solar-rechargeable battery-powered maintenance robots + local, automated robot and satellite construction facilities

One the infrastructure is in place, no more labor needed.

The above have already mentioned all the good answers, but here's another possibility for an actually tradeable raw material:

Nuclear (fission) fuel; no matter what sci-fi process you use, you're not going to transmute anything cheap into nuclear fuel without using even more energy than you could practically get out of it, it's basically not available anywhere in the solar system besides Earth (ore-forming processes make it actually accessible at reasonable concentrations) and it's got so much energy per mass that it can still be profitably shipped out from Earth's gravity well.

And if matter transmutation is just for turning elements into other elements, rather than Replicator-like creation of specific designs from anything, finished and processed goods could still be traded. Especially stuff like high-end microchips - they're really light, but require an incredibly expensive processing and supply infrastructure to create - and not because the materials to make the chips are at all scarce.

Such a time is probably another great filter. Either society at large finds something to pursue as valuable, or collapse entirely do to apathy. Great hook for a space opera imo.

And at that point humans are no longer needed.

this

Entertainment and Traditional goods if we're in a utopian society.

But then you have the problem with stagnation and regression.

People generally get good at doing things out of necessity, sure you might get some smart people here or there keeping shit in check, but if something goes really really screwie with the whole shebang you pretty much set your self up for societal collapse.

STDs

Humans aren't NEEDED to begin with.

A body still needs a brain.

>Colonizing planets.

Waste of resources.

There's no resource in existence that justifies interstellar trade.

Because 'cheap matter transmutation' can have its own limitations based on the specifics, (as pointed out by other posters) - I'm going to answer the question as best I can based on the following assumptions instead...
>FTL exists and the fuel for it is the only thing that can't be transmuted.
>There is not a need to trade any other raw material or consumer good, such things can be made domestically for an extremely cheap cost.

Under these assumptions, I don't think planets would trade anything with each other besides FTL fuel. I'm going to assume that FTL travel also applies to information and data. Because the labor pool that would ordinary be making consumer goods or gathering raw materials no longer needs to do so, they are free to follow other purists - such as the sciences or humanities. I would imagine that such cultures would freely share their information and artistic endeavors, as there is no longer a need to 'sell' your art or information.

People trade because they're both trying to better their situation by getting something they want by giving away something they have. But because you can have anything you want without needing to give anything up - there is no reason to trade. There's no reason to work or toil to produce anything, nor is their pressure to create something profitable.

OP, you live in a world where people spend millions of dollars in micro transactions on totally cosmetic digital items like exotic weapon skins and hats.

Even a post scary city society people will find brand new "item of scarcities" no matter how artificial the scarcity is.

Even if you could pull an exact molecule to molecule copy of the Mona Lisa out of thin air, you'll still get art collectors wanting to trade to own or I'll even just see the original. Even if the only thing they had to trade with other works of art.

Actually do that. Your story set on the USS Louvre. The most Advance Explorer class ship the fine art community has created. It's ongoing mission, to collect and catalogue, to seek out and find new works and buyers, to boldly critique where no critic has is critique before.

Spice