I'm thinking of lowballing a guy asking for selling advice - so I could buy said thing cheaper
What makes you want to cheat this person?
He is a window shopper who cant decide on what to charge
You should not try to be greedy in dealing with this person. It is best to be fair and treat others how you would want to be treated in a transaction.
Why should I, my time is valuable. I have to consider my own needs before the scammer.
It's wrong to call this person a scammer, because they merely asked for your honest opinion. You are the one who is trying to cheat in this transaction, and if the seller asks around for a second opinion, he will realize that and refuse to work with you at any price.