Honoring Deals
Never betray a standing deal.
If you ever find yourself a deal better than the deal you got yourself into, then either end the existing deal (and all the repercussions that come with it- like loss of security deposit etc.) or don’t take the new one.
Dealings should be direct and honorable. If you are speaking to a buyer for a product; don’t jump levels and start speaking to their vendor.
You might save some money but this is going to cost you time, hassle and your relationship.
Also, if you ever see that a deal worked out badly for you, don’t make a big deal about it. Just remember and don’t repeat.