Site24x7 (from Zoho's ManageEngine) is an all-in-one console — website monitoring beside server agents, network-device monitoring, APM, cloud and log management — and that breadth is the reason the pricing reads like a tax return. Plans bundle monthly quotas of 'basic', 'advanced' and 'network' monitors that refill but don't roll over, and you patch the gaps with à-la-carte add-ons.
The sting is in the fast checks: the cheap ~$9 Web Uptime plan polls every minute, and 30- or 10-second intervals are reserved for Enterprise tiers running into the hundreds of dollars a month. 247Monitor charges £9 for 30-second checks, a real-browser journey and a status page — and the price on the page is the price you pay.