But theoretically if the share is expected to go up at faster than the rate of compounded interest at the current interest rate, then it's a better deal for the seller to instead take out a loan using the share as collateral. And if the share is not expected to go up at faster than the rate of compounded interest at the current interest rate, then it might be a better deal for the buyer to loan out their money instead. The only thing that would make this a worse decision than the share trade are middleman costs.