Hello @fbal and welcome to the community,
You are correct in your assumption that business plans are more expensive than the personal plans.
I believe you may be confused with the current difference between business and personal plans.
-
Business plans, such as Teams or Enterprise are priced per user/month on an annual basis, or a slightly higher cost if billed monthly
-
Personal plans however are only billed yearly at the price advertised, currently either $10/year for a personal premium plan, or $40/year for a families plan (which also provides premium access to your personal account) and is needed for sharing items in a Families Organization between individuals.
With the Families Org you can share with up to 5 individuals (including yourself, so a total of 6 members). Breaking it down that works out to $3.33/month for the Families plan, or only ~$0.56/month between 6 family members.
As far as I understand the Teams and Enterprise plans provide some further features, specific to business use-case (such as Event logs, User groups, Directory Connector, etc.)
You may also wish to look at the Bitwarden Help section regarding the current plans and further details.
Regarding TOS, I believe a business using a Families plan would most likely go against acceptable use. Though the reverse should be fine, being that a Families plan is limited to 6 total members, if you need to share with more people than this a personal Families plan could upgrade to a business plan with no maximum user cap.