For $10 their cost for someone constantly typing new searches is significantly negative. It's surprisingly expensive for them to do a search and doing 1 search every 30 seconds for 8 hours is ~3x more than the cap of their $5 tier. I'm not saying that's a reasonable usage case for me I'm just saying the limit on profitability occurs SIGNFICANTLY sooner than "as fast as you can type for a month".