A tempting offer no doubt. Save money on some work you're getting done.
But what's going on here is that somebody is saying to you:
"Hey, you know that agreement that we have as a society where we all pay a set proportion of our income to fund the services that we all use? Yeah well I'm not going to pay all of the amount that I owe. But listen I'll split the difference with you by giving you some money off my charge. That way we both win."