Not really. With the CAL system you pay per usage. Without that system the
standalone server product would be much more expensive to spread the costs
(or collect the earnings, whichever way you would like to look at it). This
would result in the server product becoming too expensive for SMB's and only
affordable to large companies.
Also note that we are not talking about client/server OS's and client-server
access here. This has nothing to do with the CAL system accessing the
Exchange services from a client computer. This can be any client (even
non-Microsoft based) capable of making an Exchange, POP3 or IMAP connection
or has a browser installed.