The margin of profit is up to 300% depending on different factors which are :

Very much depends upon the location where you want to do the business. For example in most parts of India computer motherboard scrap rates are 6 USD/ Kg. but in most parts of Africa, American countries, European countries, Malasia etc. for 1Kg. scrap computer motherboard you have to pay only ½ USD.

The percentage of profit depends upon your location as well as on your marketing skills.