$10, or even the $40 plan, is a negligible cost to even a 1-man operation, and to a "big ticket" company, it might as well be free. So don't even take into consideration the cost. Keep in mind "open source" software isn't actually free, you have to pay an engineer to install and maintain it, learn how to configure it, fix it when it breaks, etc. Those costs are easily higher than $40/mo even if someone's only spending 15 minutes a month on it.<p>What Pingdom seems to be offering is a (basically free if your business isn't being funded on a credit card) service that requires very little time and know-how to maintain. Clients probably chose it because their time is more valuable than the monthly cost of the service. Contrast that to open-source, which is perfect for those who'd rather spend extra time than extra money.