I think the source depends also. When most of my miles were just a work perk I didn't really think about their value too much. I also was a total novice and just knew enough to keep things from expiring.

Now that I am picking and choosing credit cards for bonuses I have to assign values to them in order to pick the best offers. I am relatively conservative in my values, based more on what I'd spend than an aspirational value.

That said, I am an accountant and I take a little too much pride in the spreadsheet that I have cobbled together to track it all.