There are two problems with hitting a plateau @ 300K: Housing costs and College Tuition.
At the traditional 3x debt to gross income metric, your home mortgage would be capped around ~$900k, vs the $1.3-1.5MM range of current trading prices. Which is not terrible if you lock something in. However, once you are at 4x paying for schools becomes a far greater challenge. You could be looking at anywhere for $175-250 per kid. So, capitalize this and you are at $350-500K. That is, your combined "future obligations" would be something in the range of $1.7 to $2.0MM (exclusive of retirement). Which is something closer to 6.5x gross income. Which is pretty highly leveraged. You're after tax cash flow without real-estate tax shields could easily be ~200k, so you are looking at something like 10x cash-flow leverage. That is about as high as most PE guys will take a decent c-corp.
Just start shielding your income and assets as soon as possible. Strategize to minimize exposure to asset inflation (housing, education). The IRS (tax man) and the "doo gooders" in academia (ironically, the new "alternative minimum tax" man) have really boxed in the middle class (read: the not-rich enough) from the perspective of lifetime earnings. Most of your "savings" will be at risk to get swept from you, thanks to "financial aid" effect driving college tuitions.
These numbers get bounced around every now and then but they are worth considering. Inflation in "raw materials costs" for knowledge workers (kids) need to get passed on to customers (ie, employers) if you want to stay in the same place (red queen effect and all that).
This is relevant when you are evaluating career moves down the road.
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3 bedrooms (Weekly Average Prices, San Francisco)
$1,339,274 $1,573,313 $1,805,297 $1,720,736