BTW , I make over $150K a year. My wife is a CPA and has a very successful business. We pay lots of $$$$$ in taxes each year. We have never been on welfare, always paid taxes. I haven’t even taken a single sick day off in the last 10 years. If the US government wants us to leave - So be it! I’m sure we will find happiness elsewhere.
That pretty much guarantees the 601 waiver will be denied. Obviously you won't face extreme hardship if she left the US (being separated from your spouse may be a hardship, but not "extreme" hardship by USCIS standards). Hardship waivers that get approved are those where the US citizen is highly dependent on the immigrant, usually due to severe disability or disease, and thus would face death or greater illness if the immigrant spouse or parent left the US.
But anyway, 601 waivers are really a last resort only after all appeals have failed or you've given up on appealing further. So you're a long way before you seriously think of the waiver. For now, you have the following stages:
1) before denial, convince this IO that your wife did not have unlawful presence before taking that trip to Mexico. Find a lawyer ASAP to write a letter explaining that she was only out of status for the 187 days due to the F-1 D/S and all that, not unlawfully present. Get the lawyer to keep the letter to one page (with maybe a few more pages attached if quoting a regulation or USCIS memo or court precedent), not to get bogged down in 10 or 20 pages of legalese, which would result in your case getting denied or collecting dust for years because the IO gets too confused with it. This is not the stage to dive into extended legal arguments, although the lawyer might want to do that in order to rack up billable hours. The goal at this stage is to get the who IO reads it to understand and accept what is written.
2) If denied, file a Motion to Reopen. Note that the denial notice will typically say "there is no appeal", but you can still file a Motion to Reopen. The MTR should be still short and to the point, explaining why the denial was in error, as it will be IOs who read it, not judges. Note that a successful MTR usually means they put the I-485 back into pending status, not immediate approval; there may still be more months of waiting and a possible second interview. But MTR success is still good news, because if they accept it, the I-485 won't be denied unless they have another reason for denial.
3) If the MTR is denied, file an appeal with the Administrative Appeals Office (AAO) or Board of Immigration Appeals (BIA). BIA is where the lawyer can start to get into the long legalese. Note that there may be a couple of years before the case is heard.
4) If the appeal is lost, and you still think there are grounds for appeal, take it to Federal court.
5) If that fails, there are higher Federal courts, up until the Supreme Court!
6) If all the above fails, then you can look into the 601 waiver (although I have to warn that it is 99.999% hopeless for someone doing as well as you -- remember it is the US citizen who must feel extreme hardship, not the noncitizen who is deported).
I previously mentioned the possibility of the H-4 being considered invalid due the CoS being filed when she was out of status, and the old I-485 being considered frivolous based on that. While you should discuss this possibility with the lawyer, you don't want the lawyer to include arguments addressing that in the letters and motions, as USCIS has not (yet) taken that position, and bringing it up with USCIS could put ideas in their head. Right now, USCIS's only issue with this case is classifying the 187 days as unlawful presence instead of merely out of status.
And right now, you don't need the greatest lawyer who will take you all the way up the appeal chain. You just need one who can write the immediate letter to this IO, and an MTR if necessary. If anything, you should tell the lawyer that you don't plan to appeal with them, you just need this case to succeed right now so you can move ahead with your life. You don't want them to give a half-assed effort right now because they have it in the back of their mind that they can make more money by appealing later.