Last year 27K as CFI, night, IMC and PPL examiner in the UK. I made my money from a previous career and also currently have another income from another source. I would never consider working as an FI as my primary/ main career in a million years, just not financially viable as a full time job.
I know many schools now rely on instructors that have full time jobs elsewhere and do one or two days for a flying club just for the pleasure of it or beer money !!
A flying instructor is a highly skilled job with a lot of responsibility - the pay should reflect this, but it never will and this is a bad reflection on the industry.
Recently on a rainy day at my school 3 or 4 instructors were talking about FI salaries and what they thought they should be in todays market - the conclusion was - Rookie FI 20 - 25K, experienced FI 25 - 32k and CFI/ examiner 35-40K with the benefits of a normal job, sick pay, pension and paid hols. Dream on !!!