Fortunately or unfortunately, depending on your perspective, there are few statistics for nearly everything trans, and for several reasons (the desire for privacy being among them).
If your goal is to fully transition and just live your life then submitting to the pokes and prods of pollsters, grad students, sexologists and every other class of intellectual wannabee just hinders that process. And I don't believe it's simply a trans thing, either. I am part of several societal subsets and I just don't want to be bothered just because someone else has a thesis to get written. My life is just more valuable to me living it than it is being a set of data on a clipboard. Now, if I actually believed that my participation would help a trans person on their way toward their new life, that might be different.
Surgery figures are very hard to come by, and estimates are all we have. There really is no way of knowing how many surgeries are performed overseas, and besides, not every TS opts for surgery. Two good friends of mine are non-op, so the criteria of surgery does not adequately address TS issues other than those dependent on that particular data point.
So those cashiers, mechanics, doctors, etc may be pre-op, post-op, non-op, non-HRT, intersexed, etc. Yet they are trans, have participation in society and go about their business like anyone else.
I asked someone how many trans people she has met in her life, and while she was trying to come up with a number I helped her with the answer, which is "More than you think you have."