Why People sell at low cost or in loss?

Hi,

I am new and looking for to buy a domain and I have been search for some posts.

People sell .com domains at $5 – $8.

My question is when a new .com domain registration is around $10 then how they will sell at $8. It will give a loss right?

Why a loss transaction is need or need for sell. What is the reason behind this?

Why People sell at low cost or in loss?