On average, only 70% of a data bundle is actually consumed, leaving 30% to the seller to sell to other customers. For example, you buy 1MB for $0.01 (equal to 1GB for $10) and sell a bundle of 1GB for $15. Your profit per SIM will be $8 and not $5, as only 70% of the bundle is consumed, the cost to you is $7 as opposed to $10.