You can sell all that unsellable stuff you have cluttering you bag now! THe three buyers are there to buy it all!
This guy, in the Riches Villa in Undella Town, buys relics from Undella Bay and flutes from the beachcomber. THis guy pays HUGE amounts like 200000 poke!
This one is to the right of the healing counter of the
Iccirus Pkmn Center. He guy buys evolution stones, pearls/pearl chains, nuggets, star/comet pieces, and any other mineral/clay for high or higher than average prices!
This lady is in the camper on route 5. She will buy any food item (moomoo milk, castelicone, etc.) for it's purchase price. she also buys mushrooms and berries.