Every Poke, including Shinies lose their values at a horrible pace. As people catch more and more epic and shiny Pokes, they become more and more common. Meanwhile we're constantly grinding money and spend almost nothing (trading doesn't mean "spend" because the money doesn't leave the game). As more and more money comes into the game and less and less leaves it, more and more money will be in the hands of the players.
The rich players collect incredible sum of money, but meanwhile they already bought every strong Pokemon they wanted, so they won't buy another shiny Bellossom for example. As a result, the value of good/shiny and relatively common Pokemons drop rapidly, meanwhile the price of good but rate pokes (mostly UCs and dragons) rockets into incredible heights.
I wish I would be an economist where this leads, but my guts tell me that it means that shortly only shinies will have value on the market. And that you won't be able to have a really good UC, because the rich players will offer such an irrealistically big sum of money for it that you won't be able to say no.