The best analysis in a 14ers.com thread was 1 in 30,000 chance of dying climbing a 14er, while 1 in 400,000 chance driving to a 14er trailhead. About a factor of ten difference.

CFI estimated 319,000 summits of 14ers in 2016 with 11 dying so far in 2017. That gives the 1 in 30,000.

NTSA says the recent US auto death rate is 1.25 in 100 million miles. Assuming the average 14er drive is around 200 miles (between Denver and Buena Vista, the most frequently climbed 14ers) gives 1 in 400,000.