SAN FRANCISCO -- The technology boom hasn't made San Francisco unaffordable for just middle- and lower-income households. Technology workers are also struggling to afford the soaring cost of living in the city. Entrepreneur Jon Wheatley moved to San Francisco from the United Kingdom four years ago. He says it was the best place on the planet to build his startup DailyBooth, which was one of the first photo-sharing services, and for a time, the most popular one. With the rise of Instagram and other photo-sharing services, DailyBooth sold to Airbnb and shut down in November 2012. Wheatley is now working on another startup, Need/Want, that he is funding himself. But he won't be doing it in San Francisco. He's trading the Golden Gate Bridge for the Gateway Arch (and the balmy weather for a real cold snap). Two days ago he left behind his $3,900-a-month one-bedroom apartment in the trendy South of Market neighborhood in San Francisco to join his co-founder, Marshall Haas, in St. Louis. "It had just become too much of an expense," Wheatley said. I could no longer could justify it. So I decided to move somewhere cheaper. He says St. Louis is a vibrant city with an up-and-coming startup scene at a much more reasonable cost of living. Wheatley is now renting a two-bedroom apartment for $1,200 a month on the main drag in downtown St. Louis. And he and Haas pay just $300 a month to rent space in an office building filled with 75 other startups. The tech boom pulled San Francisco out of the recession. Unemployment in San Francisco has plunged to 4.8%. But there is a downside: rapidly inflating prices in what is already the most expensive housing market in the country. "I have nothing bad to say about San Francisco at all apart from how expensive it was starting to become," said Wheatley who blogged about his move to St. Louis. When you have venture capital funding, that's not an issue. But when you are trying to bootstrap a company, the cost of living becomes an important factor in deciding where you are going to live. The leading cause of death for startups is running out of money, Wheatley says. "Our runway is four times as long in St. Louis than it would be in San Francisco," he said. That's a fair trade-off, I think. San Francisco is unlikely to lose its title as startup capital of the world any time soon. "Every person I have mentioned this to has had the initial reaction that I am crazy," Wheatley said. But almost universally, once I have explained the reasoning behind it, everyone kind of gets it. In fact, one friend, Roberto Hoyos, has decided to uproot his company, Throwboy Pillows, from the also pricey Seattle and meet up with Wheatley in St. Louis. Hoyos makes geeky pillows, including "Home Tweet Home" for Twitter's San Francisco headquarters. Tech industry in San Francisco address backlash