A better one would be like:
"I'll give you 5 for it."
"I want 20."
"I'm the only buyer. 5."
"Look, it's really good, let's do 15. It's the lowest I'll go."
"No one else is going to buy it. 5."
"Come on, I need to make a living... how about 10?"
"If you don't sell, you won't make a living. 5."
"If I go lower than 7, then I'll make a loss..."
"Fine, let's do 7."
"I'll give you 5 for it."
"I want 20."
"I'm the only buyer. 5."
"Look, it's really good, let's do 15. It's the lowest I'll go."
"No one else is going to buy it. 5."
"Come on, I need to make a living... how about 10?"
"If you don't sell, you won't make a living. 5."
"If I go lower than 7, then I'll make a loss..."
"Fine, let's do 7."
"I'll give you 5 for it."
"I want 20."
"8 is the highest I'll go."
"It's really good, you should go for 15."
"It is good, I'll give you 10."
"Deal."