Assuming it's the network impact you care about, that's precisely the metric that matters. Your network does not care how hard SQL Server had to work to create the query, only how much data it had to pass through. The only other question I can think of is, how much data do you SEND, for example, if your database is supporting an internal web application of some sort, then is the SQL Server and IIS on the same machine and, if not, how are requests sent to the DB, and if, for example, you need to insert 10 rows, do you send one request to the DB, or 10 ? You can track the number of transactions made in a time span ( but of course, not all transactions are the same size ), but in general, just tracking the network traffic seems like the right port of call to me. Just remember to track it in both directions to get a real picture.

http://blog.sqlauthority.com/2010/10/04/sql-server-find-total-number-of-transaction-on-interval/