@Poptard  
Dragons have eaten gems long before My Little Pony existed.

Remember, Gems themselves aren’t currency, Equestria uses coins for currency (Commonly reffered to as Bits). The gems are probably just worth a varying amount of bits. Rarity’s gem was worth quite alot of bits.

Made in Chineigh?

The owner of the dryer sold super cheap because he loves sight gags in cartoons.

The medium blue one only bought a cart of donuts.

@Poptard  
IN A INEFFICIENT MANNER!

HE EATS MONEY!

Most likely the value depends on the gem’s type. As in most kinds are cheap, but a select few are worth a small fortune.  
So I guess rubys would be one of those.  
And Spike gave that one away first since he walues quantity over quality / all gems taste similarily / a gem’s worth isn’t correlative to it’s taste (and Rarity isn’t a dragon to know these things), I guess?

@Background Pony  
Nah… I dislike this but for the general plot of “chacter trying to be cunning and cannot handle it”
 
@Dr Outback  
I’m not really complaining to be honest. At least not about things made with rule of funny. But come on, everybody in fandom gets to over-analyze stuff. Why economist can’t have a shot ;)

Might I posit that they’re just RENTING it?

if you look at that machine you can guess that it was bought somewhere beyond equestria OR from some humans via some broken 4th walls

A tonne of salt is worth considerably less than a carat of diamond.
 
Not all crystals are created equal.

@Pathfinder  
All and all, this is supposed to be a joke.

@Pathfinder
 
I sure hope you don’t dislike it JUST for that…

@Pathfinder  
maybe you should stop over analyzing ponies

Ok - I give up trying to understand economy of MLP. I was sure that jewels were cheap commodity that are only valued for their aesthetics and are used only by fashion designers and so on. Now we see it is valuable as hell and accepted currency - maybe there is no real correlation between their size and their value? Maybe, I don’t know… store magic or something. Gha… I’m confused. After my finals I gotta sit down and try to come up with decent model. Why 95% of tv shows, even clearly for adults, don’t put any thought in the economics. Sorry for rant, but this episode I dislike..

I really hope that dryer appears again in the future. I wonder what other crazy add-ons the CMC are going to buy for their club house.

We don’t know how much the others are worth. None of their recipients spent them on anything.

So basically gems aren’t, as suggested by previous episodes, a cheap, plentiful commodity.
 
Spike must be costing Twilight a fortune!

Gems as currency….  
Gameloft reference anyone?

HA! Rarity jewel was the most valuable! where is your “worst pony” now bitches?!

did the CMC tricked Dr Eggman into believing that was a Chaos emerald and got his machine?

Say what you want about Rarity, she knows the value of gems.