“Startup idea: Coinbase but show users the cost basis for all their holdings”

https://www.cointracker.io/ ? I just assumed Coinbase would acquire them at some point.

There's actually some cool apps people have built around this that I should have mentioned in the blog.

Here's one for example: https://noahlitvin.github.io/coinbase-costbasis

Personally though, I like to do these things in a spreadsheet because it's easier do another "query" or "analysis" on top of it.