How would you describe it? How does it compare to say, Cherry Creek?
Boulder probably has more startups per capita and aside from a few whales like Google and Ball Aerospace, it leans more towards startups. This is partly because once a company grows beyond 100 people or so it's too expensive to find office space in Boulder, so they move to Longmont or somewhere like Broomfield along the Boulder-Denver corridor.
Denver has lots of tech startups too, but also a lot of enterprise-y companies like Charles Schwab, Comcast etc. I personally prefer Denver because I'm a city person, but I lived in Boulder for 15 years and really liked it as well. I may even move back there at some point. I still own a townhouse there; it may end up funding my retirement.
Seattle doesn't appear to be markedly cheaper than the East Bay. If you want out for cultural reasons, sure, but the cost of living differential appears marginal (and the gap will only close as tech hiring there continues).