How to handle the lower offer

I received an email from a guy who said he is a webmaster. He want to buy some text links on my site. It is another site, not this Blog.
The first question is Price?
He replied with some sample of this kind of ads he called it text link. Actually it is contextual link ads, which is a paragraph including 4 links.
And the price is over my imagination. He offered US$ 15 for lifetime each paragraph. There are 5. So Total is $75.
I have to decline it immediately with following message:

Sorry, I have to say the price is too low.
I normally charge $15 per link each month.

I think the price gap between us is so huge that he will quit. I am still wrong.
He replied and sent me a long analytic about the market and gave another offer.
$100 for the deal of 5 years in total.
So I said no, he gave another offer. I said no again, he gave another one offer.
Finally, he offered US$ 125 for the deal of 3 years and there will be 5 links in each paragraph, and total 5 paragraph.
It is still only 125/5/5/3/12= 0.12 per link each month.
I ask for $15 per link each month. I don’t want to waste time.
I have to deny it very clearly. It may hurt his heart. 🙂

I think we should close this kind of discussion. You can not accept my minimum price. So it is end. Do not waste your time and mine.

The actual market price is not same as what he said. I sold many text links. The lowest price I sold before is $15. The latest price is $30 I sold this morning.
So I want to announce that purchase text link on my sites only when you have $20 per link per month offer.