https://coldsignal.io/2026-06-21https://coldsignal.io/beehiiv-vs-substack-paid-revenue-2026/2026-06-21https://coldsignal.io/beehiiv-vs-substack-who-keeps-more-newsletter-money-2026/2026-06-21https://coldsignal.io/kit-vs-beehiiv-vs-flodesk-2026/2026-06-21https://coldsignal.io/substack-vs-beehiiv-paid-newsletter-fees/2026-06-21