You should probably base your understanding on what she wrote:

I take it as a given that everyone knows better than to quit their job - any job - to take up cracker-baking, so I attached no value to time. I happen to love messing around in the kitchen.

It is primarily about the taste, not about the cost. You are to understand that she willingly spends lots of time in the kitchen and would get satisfaction out of making better tasting bagels, that just happen to be cheaper. I'm rather happy with the fact that my girlfriend insists on baking our breakfast cereals herself.

But it's presented as being about the cost.

Sometimes, getting away to do something different is a better use of time than sitting staring at a problem you've been stuck on for hours.

That is actually an intersting question. Put in hacker terms would you say rms' time is worth nothing?