The problem that faced by classified websites

Those classified websites like ebay.com, lelong.com, mudah.my, alibaba.com are facing the same problem from beginning until now. Actually all of them want to charge the seller by 1% of total sale. But the problem is when the seller deal with buyer outside, as long as the buyers has the email address or phone number of buyers, sure they will deal outside like bank in or cod and the buyers won't click on "buy" button on their website. If buyers don't click on "buy" button, then website admin CANNOT know the price of sale, so CANNOT charge 1% fee from the total sale.

And all the websites admins don't know how to prevent sellers and buyers deal outside. That's why those websites won't charge 1% of total sale but charge the advertising fee! It is very unfair to sellers, the sellers spend their time to write and post advertisement onto the website and yet the website still want to charge them money, so not only they lost time post advertisement and also money too! The worst thing is if they cannot sell out the product after they advertise on your website, they will wasted their money for NOTHING!

So my website won't charge fee for advertising, I charge 1% of total sale. For example, when the seller success sell out the item at USD100 from my website, I earn USD1 from the seller. So it is fair to the sellers, because if the seller can't sell out the item, he don't need to pay anything to the website admin.

I spend 2 years to figure out the solution, but I can't think of any solution. Previously I figured out few solutions but all of them don't work. For example :
1) Don't allow seller show the hp number and email on their advertisement, this solution won't work because it will cause inconvenient communication between sellers and buyers, think about it when the sellers have many questions about the products and when the sellers want to COD, sure they need hp number of each other to communicate to each other.

2) Free gifts will be given to the seller if the buyer click "buy" button, this solution won't work because the free gifts are not worth than the 1% of total sale, the sellers will ignore the free gifts.

3) 10% discount will be given to buyers if the buyers click "buy" button, this solution won't work because it will be very inconvenient for sellers to state the price of item, and if the item price is 10% expensive than the real item price, the buyers will misunderstand the item that advertise on my website is expensive than ebay.com/ lelong.com/ mudah.my and thus the buyers will not buy it from my website and they will go buy from other websites.

Since 2 years until now I keep finding the solution for this issue. Finally today I find out a perfect solution to prevent sellers and buyers deal outside. Now I can earn profit of 1% of total sale. Sorry that I can't tell you the idea / solution. If you are interested to know my idea or solution, you have to pay me RM10,000 then only I will tell you the perfect solution.