But if you want to look at some attempt at an actual multiple – though of course it’s based on a model and not empirical observations, with all the limitations that entails – you can look at item “c” in figure 5 here:
https://www.nature.com/articles/s41586-020-2923-3/figures/8
There you see their estimates for additional infections compared to not reopening per POI, not per category. So, in other words, what one restaurant would contribute, on average, compared to one grocery store. The differences in that chart aren’t anywhere near 100 times. They are much, much closer to 10, if not half that.
I don’t pretend that this study is the final word on it, or anything of the sort, because I can see the obvious limitations the study has. But I also can see that they are making a strenuous effort to do something besides guess (or I suppose as you put it, ‘make numbers up’), and they aren’t arriving at anything remotely approaching 100 times.
I am very happy to have an honest discussion about it, which is why I asked if you had seen something that would support a multiplier of 100. In fact, I’m still eager to consider it if you have. Have you? Or is that just a guess.