Actually there's more than one. Cloud computing is much more efficient. When you buy a graphics card, it's going to collect dust 90% of the time, that doesn't happen in cloud computing.
You only need a tenth of the power to achieve the same gameplay experience in a cloud as you would if each gamer had to buy a separate setup.
Consider 1000 gamers each with a $1000 PC, the combined cost here is $1,000,000. In a cloud the price is equal to the max percentage of gamers online at any given time, so if no more than 10% are logged into the cloud at any time, the cost would be 10%.
Then there's also the factor of idle power even when you're playing. If gamers uses 50% on average of the GPU's capacity to run the game at a predefined framerate, that will cut the cost in half, lowering the cost to 5%.
Once you have the technology to do it, there's big money to be made in cloud computing. The question is, who's going to benefit from these huge savings.