I'd try to just respond to the in-law's by saying how proud you are of your wife, how excited you are for her, etc. Just re-enforce how awesome their daughter/sister is – which may really be what they want to hear – and try not to think of it as a comparison to how you are. Granted, they may mean it as a comparison to you, but take it as a praise of your wife (which you probably agree with), refuse to acknowledge any dig to you that they may mean, and that should make it the conversation pass.
As to how to deal with it outside of the conversations with the in-laws…as others have said, remember that you're a team, so her success is your success. And the whole apples-to-oranges things. Also that you're simply different people, with different skills and strengths. I don't have in my family any couples that make the same or even similar wages. Most of my family is stay-at-home moms, so most of them the husband is the only one with an income. Some the wife has an entry-level or other low-paying job, and the husband has a higher-paying job. Situations where the wife has the higher-paying job are historically more unique (and my family sticks to the historical trend), but statistically it is becoming more and more common. Between my long-term boyfriend and I, I have the higher education and the substantially higher paycheck, but we deposit our paychecks into the same bank account and view it all as “our” money. The only people who care who makes more are the IRS and a couple family members that I'll give a quarter and they can call somebody who cares. It's crazy that people still make a big deal out of a woman making more than a man, even though opportunities are pretty level, if not in favor (at times) of women. I know, views vary on that 😉 but there's arguments on both sides.
So, I don't have the “how to deal with your spouse being more successful” issue, cause I'm on the opposite side…but I do have the “how to deal with the woman making more money” issue, and my answer is just stay above the issue. If people comment on her success, applaud it. If people ask about what you make, there's no need for you to answer. If your wife has an issue with your making less, then you and she need to have a discussion about the issue, why it's an issue, and how to address it (jumping to private may be a way to get an immediate pay increase, though may not be as good long-term). However, for anyone else, just don't stoop to their level of having the “Oh, so your wife makes more?” discussion. It's not worth your time to pander to their silly ideas.
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