It is a supporting channel, and that is fine
For most businesses here, WhatsApp is the main road and Telegram is a useful side street. Treating it as a whole separate operation, with its own person and its own spreadsheet, is what makes it expensive. In one inbox it costs you nothing extra.
Bots are cheap and instant
No verification, no documents, no waiting. You can have a Telegram bot answering your price list before lunch, which makes it a good way to test automation before you commit to the WhatsApp API.
No per-message charge
Telegram does not bill per conversation, so high-volume support, class reminders and community broadcasts are effectively free. For a school with two thousand parents, that difference is real money.