XYX is above $55 at expiration
If XYX is trading above $55 at expiration, it is likely that the investor will be assigned on the written $55 calls. Consequently, he will be forced to sell the XYX shares at the strike price of $55. Remember that when call options are written against a long stock position, an obligation to deliver those shares at the options' strike price is being assumed. If a buyer of the same calls decides to exercise, then the writer must deliver the shares if assignment is received.
In establishing a collar, the obligation to deliver shares was assumed so that the call premium could be used to partially offset the cost of the put option. The stock being called away at $55, in this example, represents the investor's best-case scenario. A $10.25 gain (the exercise price of $55 minus the original price of the stock, $44.75) will be realized less the $0.25 cost of the collar. The upside, therefore, is limited to $10 per share.