>>mikece+(OP)
Signal had 40 million active users in 2021 [1]. With 14 million in infra cost, that comes to .35 per user/year. Total expenses are about 33 million, so about .825 per user/year. All in all that seems very reasonable.
>>umanwi+9z
Pay attention to WhatsApp's wording (all privacy/security claims start with "your messages"), and their privacy policy, and you'll see that while message involving with individuals (non-Business users) are secured, your contact list is not, neither are chats with businesses or the metadata about you chatting (destinations, frequency, time)