I have spent a TON of money on transition. In terms of "passing," by far, the best money I spent was with the speech pathologist. Besides the confidence, as just one example, I was at WalMart yesterday picking up passport photos I had sent to them. I was in total boy-mode. No makeup, no wig, just ball cap, sweatshirt, and jeans. In my normal "girl" voice, I asked for the photos. the clerk turned to another clerk and said, "She wants to pick up passport photos." The other clerk says, "I can help her..." ok. The ears are pierced. But the little steel balls in my ears and my voice were the ONLY clues I gave the clerks, and both somehow thought "woman." I think the voice was everything.
I should mention too, that my speech pathologist actually turned out to be an expert in transgender voice. And, not "voice lessons." Straight up medical professional. She did her Master degree at Johns Hopkins, doing work with transgender MtF people. She LOVES to work with MtF folks. In my opinion, THAT background and experience made a lot of difference.
Anyway, my speech pathologist was literally life changing. Highly recommended.
Kate