For sure it isn’t pleasant when I have to I have to pay $ 7,500 in taxes on a weapon mod sold for $ 37,500.
I rather see that $ 7,500 as a commission to the marketplace for getting advertising, distribution and a secure trade.
You could easily sell your stuff via your mailbox but have to advertise and distribute your goods to sell on your own and you won’t have the security to receive your earned ingame money.
The marketplace taxes should be lowered, especially for higher priced goods.