Game Theory - Application to Banking and Finance

Yes, because once the demand is served according to the original price, IBM has an incentive to decrease the price to serve customers with a lower reservation price.

Then repeating the decrease again & again until the prize equalizes the marginal cost.

Yes, some customers with a reservation price above the original may still prefer to wait a price decrease. (because they know it will decrease)

When the computers are rented, any price decrease cost a higher amount because the decrease applies to all computers, not only the ones in the IBM stocks.

Renting rather than selling allows IBM to credibly commit to not decrease the price. Customers have no more incentive to wait any price decrease.