When Astro Teller, head of Google's secretive Google X research lab, addressed a Vanity Fair gathering of the technorati in San Francisco last month, he said convincing people to wear a smart device on their face or any part of their body is a "tough" sell.

How tough? Companies need to make devices useful enough to compel you to attach them to your body, he said at the time.

But there's another catch: Wearables, from Glass to smartwatches, also need to be cheaper -- a lot cheaper -- before they go mainstream.

"Every time you drop the price by a factor of 2, you roughly get a 10 times pick up of the number of people who will seriously consider buying it," Teller said in an interview at Google's Mountain View, Calif., headquarters. That means "two more rounds of halving in price" for most wearables before they're an attractive buy.

For certain products, like $30 or $40 pedometers, a big price cut probably won't make much of a difference, he said. "But for a $200 watch, or Glass, or anything in between, I think it's sort of fair."

For Google Glass, which costs $1,500 today, cutting the price in half twice would mean a drop to $375 -- though the company said it couldn't comment on a price target or timeline for any cut. But Google, which generated almost $60 billion in sales and $13 billion in profit last year, could absorb the cost cut -- if it did want to make Glass a mainstream gadget rather than a novelty. Analysts who dismantled the eyewear and appraised the value of the individual parts pegged the total costs of Glass' components at up to $150. That means, right now, Glass seems to be selling for at least a 900 percent markup.