if an employee came into my office with a "beat what I have or I walk" I tell him to walk as this is not a person that has any loyalty to my company, and I look for long term people.
first off, for all I know, it could be bullshit. Second off, what's to stop him from doing this every month if I cave to his idiotic demand. If some other company is in a position to pay him a higher salary, then good on them and good on him for finding such a place.
I personally prefer keeping the people I work with than training new people every couple of months. It is just bad business.
Loyalty is dead in today's age and that is really sad. Whatever happened in being proud of where you worked, who you worked for, and what you did! Everyone is a money chaser, and honestly, if I see a CV where a guy has been job hopping, I won't hire him due to the fact that he might abandon me in a critical time when I actually DO need him for peanuts more per month.
It also shows weak character that you couldn't walk up to your boss to discuss your current "unhappiness" to see if there is a mutual agreement you can reach, instead, you took the trust, shat all over it, and went job seeking behind the company's back without trying to find a solution in your current work place.
Whether you think so or not, they taught you skills, gave you experience, took the time to entrust in you and because of them you are now worth more in the market. The least you could do for them is try to resolve things, especially if they haven't wronged you!