I agree with @Alysa that $55K is Austin is low. But with negotiation (to increase base), and bonuses, and stocks, or other perks, it can be viable.
I think @vivian brings up a good point, though, that what you care about in your life, matters the most in making this decision. Are you thinking about family, and a large home, and being able to relax? SF provides almost none of that, for example. It has the lowest children per household of any metropolitan region in America, 3 bedroom single family homes can run you $2.5 Million, and there is definitely an atmosphere in the downtown and financial districts during working hours that has a high intensity bustle to it.
If, however, you don’t care about any of that, and are okay splitting an apartment with roommates, and have some food catered at work, or are good at cooking, $110k in SF can take you very far, where you can even be maximizing out your 401K every year (side note, everyone should aim to this if financially possible, this is a very sound financial decision; we should definitely have some posts where we talk about the intricacies of finances).
I just came back from a trip to Austin, a city I really enjoy (also visited San Antonio, plus heading to Houston for the first time very soon). I think you’re from Texas, right @lizhoucheng, so I don’t need to write much about Austin (although, Austin is clearly different from the rest of Texas). From my limited experience there, though, the tech scene is nothing like downtown SF, or South Bay in California. The people move at a different pace, and the everyday topics people talk about are different. But that’s also what gives every major city it’s unique character. The people of Portland are not the same as New York are not the same as SF, etc. And to me, that’s an amazing thing, and reason why I love visiting all of those cities.
In any case, I think it’s important to really spend time thinking about what you value in life, and once you have the weights of what’s most important, you’ll be able to make the best decision here.