Hello Ashish,
It is an interesting question, that will depend on type of license you have purchased. Depending on your agreements with SAP.
SAP does different types of agreements, to my knowledge SAP does the following:
named users - this is user based, so a named user license allows you to access any number of sessions (so in my opinion this would be costlier), although I must admit I haven't been privy to any numbers in my organisation.
volume based - This is for e.g number of data objects created in your production system, for example in an insurance system its the number of claims created in SAP in a year. You buy this when your userbase grows and shrinks based on your business volume.
Concurrent Session Based - This may interest you, since you use BI.
I found a blog that explains few concepts, have a read.
BI Platform Licensing Basics: CSBLs and Named Users
Get in touch with your local SAP Licensing team, they should be able to guide you better.
Regards,
Siddhesh