Depended on the version of SQL Server 7 you were after.
The only one I can remember for sure was the Desktop edition which could handle 5 concurrent connections was free with some restrictions.
The you had standard and enterprise editions which had a huge price difference and I cannot remember the CAL price since you mention 5 users.
You possibly could dig thru the google groups and find an old post with the information or even find the old pricing info thru a cached google copy but I had little luck with anything concrete.