the lawyer used the processing time at the time you applied for citizenship as the rule of thumb. for me, the processing time when I applied for citizenship was 19 months. my waiting time was way over that. the total fee was 4k including tax. it was very straight forward. I went for consultation, lawyer spoke with me for 10 minutes, then his assistant helped me prepare the case. within two hours, all the working papers were ready. I paid the fees right away, the next day my file was dropped to the federal court.