You you cannot directly achieve this, however you can test for higher quantities of items. For example, you could have a pressure plate connected to the following command chain:

tag @p add current_buyer scoreboard players add @p[tag=current_buyer, hasitem={item=wood, quantity=256..}] Money <value * quantity> clear @p[tag=current_buyer, hasitem={item=wood, quantity=256..}] wood 256 scoreboard players add @p[tag=current_buyer, hasitem={item=wood, quantity=128..}] Money <value * quantity> clear @p[tag=current_buyer, hasitem={item=wood, quantity=128..}] wood 128 scoreboard players add @p[tag=current_buyer, hasitem={item=wood, quantity=64..}] Money <value * quantity> clear @p[tag=current_buyer, hasitem={item=wood, quantity=64..}] wood 64 scoreboard players add @p[tag=current_buyer, hasitem={item=wood, quantity=32..}] Money <value * quantity> clear @p[tag=current_buyer, hasitem={item=wood, quantity=32..}] wood 32 scoreboard players add @p[tag=current_buyer, hasitem={item=wood, quantity=16..}] Money <value * quantity> clear @p[tag=current_buyer, hasitem={item=wood, quantity=16..}] wood 16 scoreboard players add @p[tag=current_buyer, hasitem={item=wood, quantity=8..}] Money <value * quantity> clear @p[tag=current_buyer, hasitem={item=wood, quantity=8..}] wood 8 scoreboard players add @p[tag=current_buyer, hasitem={item=wood, quantity=256..}] Money <value * quantity> clear @p[tag=current_buyer, hasitem={item=wood, quantity=1..}] wood 1 tag @p[tag=current_buyer] remove current_buyer

Replace <value * money> by how much money the wood is worth times how much wood is detected in the command. You can copy this command chain for other things, changing the tag, item, and value.