That does sound pretty outrageous. Are you in county? Can you get any word of mouth recommendations? Or ask on the eleven plus Bucks forum (they won't allow discussion of tutors but will allow pms). Ds passed the Bucks 11+ this year (no professional tuition but lots of work at home) - can you start him off with the recommended stuff on the forum (which I used) and save your money till early next year?
Also - please be very careful that the tutor you choose is fully up to date with the changes to the format. While there are undoubtedly some excellent tutors out there, some were still teaching this year's intake the old "21 question type" format right up to the exam. Absolutely useless.