Had interview scheduled through consultancy. Online coding test before the 3 face to face rounds , 1 - tech , 2 managerial , 3 - HR. But offer processing requires time

I applied through consultancy and interviewed on 19th March 2016. I was told that its a scheduled interview but it took 4 hrs for my 1st round. Management was very poor. I cleared all the rounds and was told by HR that I will receive offer letter in 1 or 2 weeks. After a week I got a call from consultancy that they roll out offer letters to all except me the reason told to me that I demanded high salary. I called HR for negotiation she told they are going through my profile and will get back to me. After 3 weeks I got a call from consultancy that people from iNautix want to take interview again. I again prepared for interview this time the interview was taken by 2 persons and it was quite tough compared to previous one. I do not understand if they don't want to select a person why they waste their time? and if once a person cleared the interview why there is need of taking one more interview??? I have not faced such a unprofessional behaviour from any company. At least don't waste anybody's time.