Okasha, I doubt you would get more selling the coin on eBay. If you know someone willing to pay U.S. $80,000 for your coin then by all means sell it to them. Keep in mind, however, that your coin is really worth about $1,500 as Josh pointed out.
Depending on the laws in Egypt governing precious metals, it could definitely be worth more in your market, but not likely to fetch you more than $2,000.
If you decide to sell over eBay make sure you thoroughly study eBay policies regarding publishing and selling from Egypt. You need to see first if you can legally list the coin for sale and check if any laws in Egypt could interfere with an international gold sale. These laws are very different from country to country so make sure you do your homework.
Obviously the best thing to do if your contact does not want to pay the $80,000 (which the coin isn't worth, anyway) would be to sell it to a reputable gold dealer in your area.