So one of the things that got me thinking is that there was has to be a sort of trade going to go on with dragons and ponies. Like there has to be something there right? With Twi and the groups of Harmony spreading peace everywhere, they got to have trades and something going on?
Well, one thing that kinda came to mind as I am writing one of my last pony based stories here, was that ponies would treat this no better than they do with each other especially natural things. Heres what I mean. What water is to anyone, any creature is universal. Clean and used to drink except ocean water. A pony could go to a lake and drink water. It wouldnt be clean but it would still replenish them and their body may filter out the toxins. But if you wanted clean drinking water, they would have to pay for pluming or pay a bottle of water to drink from.
Now, I noticed that lava was the same for dragons that they could swim and be in it, but wouldn't drink it willy nilly. Not to mention that lava cant be dirty with bacteria(Im not sure how well that holds up in the land of magic) but it certainly wouldn't help dragons just by drinking it like that.

What if... ponies sold dragons clean or... even protein lava for dragons? How the FCK they gonna do that, you ask?
Well, again the filter and clean bottled of water comes into play but instead of lava... why not melted metals and irons? Think about it, these guys probably do eat irons, ores and such to go along with gems. Its basically melted nutrients for dragons and easier for them to drink rather than chew, like vegetables and fruits being turned into juice.
Or something else like say... molecular acid. I had this involved in my Death likes me rough story but I wanted to know if others would use it too. I mean acid is just a bunch of chemicals mixed into one another. Water and lava, can mix in certain ways with other material to make acid. You can think of acid as the soda equivalent to dragons.

Now dragons could trade these things like their gems to get them. And since gems and jewels are created from volcano they have almost unlimited income. Tell me what you guys think and how you see trade between dragons and ponies could go as well as other species.