I like to go a little crazy and spend up to the cost of the table for the cart. I have a Clearaudio Maestro v2 on my hot-rodded Rega P3 and it's a wonderful combination. On my Michell Gyro SE I have a Koetsu Black and it's also fantastic. When the Koetsu dies I want an Audio Technica MC, in the $1000+ range with boron cantilever and line contact stylus.
Cartridge to turntable price ratio
How much do you spend on a cartridge before you have more cartridge than turntable. For example if you spend $2500 on a turntable and tonearm how much maximum would you spend on a cartridge? $1000? 1500?