Based on the pricing it doesn't look like this is aiming to be a replacement for mailman or majordomo public mailing lists, but more for internal private lists.

Based on the pricing it doesn't look like this is aiming to be a replacement for mailman or majordomo public mailing lists, but more for internal private lists. 150 members before you're in the "if you have to ask you can't afford it" bracket -- even small, niche projects would have more people than that subscribed to the announce list -- and that's $129/month. You could run a majordomo list with no member limits on a VPS for less than $10/month.