Yes, #5 is Etude in Black. He says to Alex Benedict, "Now, I make $11,000 a year... It would take me 90 years just to buy a place like this."

However, in Death Lends a Hand, Brimmer says, "I can almost guarantee I can triple your salary in the first year." And later, a Brimmer associate who was chewed out for giving out too much information, tells Columbo the top guy can haul in about $30,000 a year. So, one can deduce that Columbo makes in the vicinity of $10,000 a year. Maybe he got a raise between the Brimmer case and the Benedict case.