Situation: 60GB production database for medium-sized company, 700+ web users during the day, some usage 7*24.
We've never thought about our system in terms of TPS... we just focus on CPU utilization on the database server. Our machine runs all 8 cores between 20 and 40% during the business day, and down to 1% overnight. Whenever utilization gets over 50% our users start to complain about speed, and it's almost always some explainable cause.
In the last 30 seconds we've been between 20 and 40%, and SQL says we've done 86,000 transactions... so I guess we're running 2,800 TPS.
We can take the system down during off hours (with advance notice) for up to an hour with no problem. More than an hour offline starts to cause real problems with the team serving our customers.
Our biggest performance pain point is trying to get big jobs done overnight. We have to sequence backup, export to data warehouse, synchs with other databases, and 45 minutes worth of database maintenance scripts so they don't run concurrently, but our overnight users always feel real system slowdowns in the depths of the night.