I qualified as a driving instructor a few years back, it costs around £2900 now, earnings are often quoted as being circa £30k in the TV adverts, what they dont tell you though is outgoings for car, student no-shows, fuel, insurance etc etc, and the training is around 10 days in total from the college, majority of it is self study at home or buddy system in your own car!
Its a lot of money for very little instruction, they just guide you really as to what to practice in the car, and no end of feedback style questions to test your own knowledge.
Plus the test fees on top, licence application etc not as expensive as what our lovely CAA charge, but still adds up to hundreds.
The FIC is much better value for money like for like, when you way up what it can lead to, and the hours in the log book if thats what your looking for, is worth £80-£100 per hour if you purchased them yourself.