To me:
- "No lo pagues." = Don't pay for it. (Lo referring to the item that you were going to buy)
- "No le pagues." = Don't pay him/her. (Le referring to the person who would be receiving the money)
But there could be nuances here that I'm glossing over.
Side question: Would you use lo or le with saludar? "Voy a saludarlo" or "Voy a saludarle"?