Isn't that how it is working? For example The cost of bandwidth is 10x less in US based datacenters, compared to Indian datacenter (despite lower wages/other costs)

300 GB transfer Vs 30 GB transfer. Who would you host your services with?

If you are concerned about your security (not that I'm validating Mailbox.org), don't always go for the cheapest options; Or as uncle Sam says

"there is always a catch junior, always!"