This is simple.
1) You only contact people if you really are going to buy the product.
This is not the mall where you are "shopping" yet are really browsing.
2) If you want to buy something, make arrangements to get it.
If it is too far away from you. Figure that out before you are taking up the seller’s time.
3) Exchange phone numbers.
This back and forth through the internet never works & people want to know you are real.
4) If it takes you more than 48 hours to be able to work all of this out you are not a serious buyer. No one is "holding it for you" while you get your act together.
5) If something is valued new at $100 or more (you know if it is or not or you would not be reaching out to them) and a person is selling it for $20 or less. Just be thankful & stop with the "what is your best price". "Can you do better." You want to negotiate bid for things on eBay