So a person contacted you unsolicited, asked if you wanted to buy something, agreed on a price and then when you went to pay, backed out?
And then had the fortitude to tell you that they were faultless?
Yeah. That's never happened to me. Here's how to avoid. Don't do business with that person. Ever.
Here is a quick summary
Him:Contacts me to sell me a clack
Me: Asks for price
Him: how does 200 sound
Me: Seems high but I will reevaluate it andn purchase it once I have the cash
Him: Okay
Me: Contacts him to tell him I am going to buy it
Him: 250
Me: You said 200 and I sold some items to get the cash for it.
Him: 250 or he ebays it
Him
welp im sorry! im really looking towards 250..have another user interested and was considering ebay posting..bet it could fetch more on ebay
Me: You said 200 so I got rid of some stuff just to purchase it.
Him
I never actually offered it for 200, i threw out that number to gauge you. another tip is wait for the sale to become official.

He did give me some tips though because I'm still new here

Him
you've only been here for a couple of months, so just some honest friendly advice is to wait until people reply/confirm trades. I've had that happen to me a couple of times, it ain't fun. I'll have to get back to you on it. I really need money right now and i'd rather get rid of an OG cherry beige set + windowed locks. maybe you have interest in that?