The Cloud owners have to make profit every month and have ongoing overheads.
A server is always going to be cheaper to buy (for a year) if the Cloud is making money. The actual real cost of both solutions is more complicated.
Cloud is OK for cross site collaboration, if you have your own local backups. Assuming issues of privacy and security are sorted (those are often unclear for the Cloud).
Cloud = Server of someone else, out to make profit.