Details: Like all Battle Facilities, The Battle Tree has a number of different shop salesmen that you can buy and give your Pokemon items that will give them competitive advantages at the Battle Tree (as well as a brand new Move Tutor). These shops even have Mega Stones you can buy for all Pokemon in the Alola Pokedex that can Mega Evolve.
Left Shop Salesman Items:
King's Rock - 32 Battle Points
Deep Sea Tooth - 32 Battle Points
Deep Sea Scale - 32 Battle Points
Dragon Scale - 32 Battle Points
Up-Grade - 32 Battle Points
Dubious Disc - 32 Battle Points
Protector - 32 Battle Points
Electirizer - 32 Battle Points
Magmarizer - 32 Battle Points
Reaper Cloth - 32 Battle Points
Whipped Dream - 32 Battle Points
Sachet - 32 Battle Points
Middle Shop Salesman Items:
Toxic Orb - 16 Battle Points
Flame Orb - 16 Battle Points
Iron Ball - 16 Battle Points
Ring Target - 16 Battle Points
White Herb - 32 Battle Points
Mental Herb - 32 Battle Points
Power Herb - 32 Battle Points
Focus Sash - 32 Battle Points
Air Balloon - 32 Battle Points
Red Card - 32 Battle Points
Eject Button - 32 Battle Points
Weakness Policy - 32 Battle Points
Choice Band - 48 Battle Points
Choice Specs - 48 Battle Points
Choice Scarf - 48 Battle Points
Life Orb - 48 Battle Points
Rocky Helmet - 48 Battle Points
Assault Vest - 48 Battle Points
Safety Goggles - 48 Battle Points
Terrain Extender - 48 Battle Points
Protective Pads - 48 Battle Points
Right Shop Salesman Items:
Absolite - 64 Battle Points
Galladite - 64 Battle Points
Glalitite - 64 Battle Points
Pinsirite - 64 Battle Points
Garchompite - 64 Battle Points
Kangaskhanite - 64 Battle Points
Gyaradosite - 64 Battle Points
Mawilite - 64 Battle Points
Gengarite - 64 Battle Points
Gardevoirite - 64 Battle Points
Sharpedonite - 64 Battle Points
Sceptilite - 64 Battle Points
Banettite - 64 Battle Points
Beedillite - 64 Battle Points
Audinite - 64 Battle Points
Medichamite - 64 Battle Points
Altarianite - 64 Battle Points
Ampharosite - 64 Battle Points
Steelixite - 64 Battle Points
Cameruptite - 64 Battle Points
Blazikenite - 64 Battle Points
Scizorite - 64 Battle Points
Tyranitarite - 64 Battle Points
Pidgeotite - 64 Battle Points
Alakazite - 64 Battle Points
Aerodactylite - 64 Battle Points
Lopunnite - 64 Battle Points
Heracronite - 64 Battle Points
Houndoominite - 64 Battle Points
Salamencite - 64 Battle Points
Aggronite - 64 Battle Points
Mewtwonite X - 64 Battle Points
Mewtwonite Y - 64 Battle Points
Metagrossite - 64 Battle Points
Slowbronite - 64 Battle Points
Sablenite - 64 Battle Points
Abomasite - 64 Battle Points
Manectite - 64 Battle Points
Swampertite - 64 Battle Points
Latiasite - 64 Battle Points
Latiosite - 64 Battle Points
Lucarionite - 64 Battle Points
Move Tutor Saleman:
Gastro Acid - 8 Battle Points
Skill Swap - 8 Battle Points
Drain Punch - 8 Battle Points
Foul Play - 12 Battle Points
Super Fang - 12 Battle Points
Stomping Tantrum - 12 Battle Points
Earth Power - 12 Battle Points
Dual Chop - 12 Battle Points
Heat Wave - 12 Battle Points
Hyper Voice - 12 Battle Points
Knock Off - 12 Battle Points
Dragon Pulse - 12 Battle Points
Liquidation - 16 Battle Points
Outrage - 16 Battle Points
Sky Attack - 16 Battle Points
Throat Chop - 16 Battle Points
Gunk Shot - 16 Battle Points
Superpower - 16 Battle Points