It is 13% of one of the cheaper components. Back in the 80s when all memory was expensive there was something of an excuse, but today we are needlessly trading the possibility for silent corruption over the multi-year lifetime of the machine for a couple of coffees. And worse, we make it really expensive and difficult for people who do want to reduce their risk by artificially segmenting the market.

Back in the 80s the need for ECC was much less because the gates were physically bigger and there was much less overall memory. Back then the chance of your computer having a bit flip was like one in a million per year, now with gigabytes of memory it's near 100% chance per year.