Later that day someone comes by with a docilely following Glass and Stone and says she might want to trade the Stone for an Ice or a Water if they've got one.

They've got salt. 

She thought they also had elementals?

Yeah but they're trying to collect more of them, they're not trading.

Where are their elementals? They aren't mages.

The mages and elementals are hidden because of the bandits.

So they're just sort of hanging out with no visible defense of their ridiculous pile of salt.

The means by which they're defending their salt are not visible, that's correct.

Seems ill advised.

Some people might get hurt trying to steal the salt but the smart ones will wonder how they got the salt in the first place unmolested and conclude there's probably something to be wary of. Even if (or maybe especially because) they can't see it.

Fair enough. Are they sure they don't want to trade?

Nope! Is there something other than an elemental she might want, they could perhaps arrange various spices and fabrics and dyes and fancy foreign glassware.

She's a mage; those things sound nice but would not do magic for her.

Then they wish her well.

She leaves.

Most mages, it turns out, are not willing to straight-up sell their elementals, till a hunter comes by with a bunch recently caught. Do they want one? He's got a Lightning and two Air and a Shine and a Fire/Stone!

How much for all of them?

All of them? Wow. He's not sure they have that much but he counts it up and names a figure. They'll need to get the salt weighed at a formal scale.

They can do that! They can get more stuff if he wants stuff other than salt, too.

Salt's nice and generic but he'd like some diversity in case some hybrid turns out to be a salt elemental and the market craters, ha ha, will they still be here and have seashells next time he comes back from a hunting trip?

Sure will!

He and his Glass (she's not for sale, he uses her to hunt) go off.

And they take the five necklaces. When he's gone - "uh, anything we can get you guys while we wait on the mage?"

...they can't talk.

...these people have popcorn, gummy candies, lollipops, and army meal bars. They set them down near the elementals in case the elementals would like any.

The elementals can look at them but can't take them.