Make Money Listing Auctions

Primary Trade or Business for Self Employment?
A person has a full time day job and pays Social Security taxes on the wages. This is how it should be and is.
The same person in his spare time sells personal property on E-Bay. This person spends 4 hours per week listing auctions and settling up orders. This person makes money on this activity. He buys low and sells high.
Does this person owe Self employment tax on the net profit? This is not his primary trade or business in my opinion. The code of Internal Revenue states primary trade or business earnings are subject to Self Employment tax. If this person did not have a full time job and sold on E-Bay full time, then selling on E-Bay would be his primary trade or business, right?
Even if the self employed income is not primary trade income, it is subect to SE tax at 15.3%.
You do not pay any social secuity tax on your income of more than $106,800.
Make Money Online With The List Auction – Profile Settings