Sometimes, when you see them, even if you don't want to buy, just buy; buy something. Support them.
Even if you don't want to use or eat what they sell, sometimes just buy and give to those around, those in need of what they sell, those starving.
Reward them for not giving unnecessary excuses.
Reward them for not being lazy.
This is not the kind of place where you negotiate prices.
They are not trying to be rich. They are trying to survive. Buy from them. Support them.
And, when you buy on credit, please pay back.
Don't even... I mean, don't even dare harass them.