Lots of variables. Already stated, how many is in a limit. Do you want them scaled then filleted? Filleted and skinned? Scaled, gutted and left on the bone? My personal preference! I like the bones and skin on, as I find they have more flavor. When I'm cleaning them for my wife and daughter, son doesn't like fish for some odd reason, I scale them and then fillet them. That take about a minute a fish. If I have a large number to scale I'll use my 30 gallon drum scaler and do about 50 fish at a time. That usually takes about 10 minutes to scale a batch. After that, If I'm filleting it will take another 30 seconds per fish to fillet. Sooooooo, I can scale and fillet 50 perch in about 35-40 minutes. That is using a regular fillet knife. Just don't care for the electric knives, as I have a hard time feeling the bone with one. This is probably more info then you wanted but your question was somewhat vague. If you have never had perch scaled and gutted with the bones in them, try them. There is definitely a big difference in flavor.
You and KP....two of a kind.I’m close behind.Rg