Depends where you live. You can make hundreds of $ a day as a street performer if you're good, and you have a good spot (preferably one with some tourists who havent managed to quite work out the exchange rate yet.)
I would like to see an A/B test with and without that chart to see what the difference in donation rates is.
I think the chart probably helps, but always better to gather data right?
I hope for the sake of their wallets that people working at startups don't take this chart too seriously. Based on the job postings I've seen in the past 6 months an awful lot of people would be paying the "rock star" rates!