Consume Product

It's actually not unproductive. People who buy and sell add liquidity to the market and they are taking on a risk because they could be left holding the bag of an asset that actually depreciated in that period of time rather than appreciated.

Imagine you are normal family man who got a promotion but in a different city. You need to sell your house to move your family. If "scalpers" don't exist then perhaps you're forced to keep your house on the market to sell for 6 months but because of the existence of scalpers you manage to sell in 1 month. The scalpers are in fact helping you in this case because now you get a faster sale and don't need to pay mortgage interest expenses and or lose the time-value of your money tied up in the equity of the house.

Nothing about scalping is parasitic. You can simply not buy what they're selling if it isn't worth the price they're selling it for.