It comes down to whether or not you could reasonably feel your life or limb was in serious danger and the person actaully was capable of hurting you. If the assailant does not obviously pose a threat to do you serious injury than using dealdly force may not be applicable and could get you into serious trouble. Then you do whatever you can to get out of the situation including complying. Your wallet is not worth the assailant's life no matter how mad you may be about it.
Unless the assailant had a knife or gun and indicated he/she may use it or I was out numbered and the assailants seemed intent on doing more than just robbing me, I would try some other means to get out of the mess. My wallet does not have any really important stuff in it so I would have no problem handing it over if that would make someone happy. I also have some pepper spray that I could use if the situation warranted it.
I asked the question of my CC trainers, if someone approached you in a parking lot to rob you could you just pull your gun and say no, get lost. Basically the answer is no if your life isn't at that point in danger. Threatening deadly force is illegal by itself unless it is done in a viable self-defense situation.
The problem is when you don't see trouble coming and you have to act very quickly. The safer bet may be to pull the weapon and take your chances. But it is why it is so important to stay alert to your surroundings. My worst scenario isn't losing my wallet but having someone get my gun, too. Then I'm not only scewed but probably someone else later on.