Dear Sir,
I have read your Project Description and first of all, this is not a copy/past message :)
I have read the overall updates but keeping the scope in mind, I am afraid that our estimate is higher, as US $750 is definitely very low budget for an App updates.
So, please let me know, if you are flexible in your set budget, we can then surely discuss further to move forward. I can assign you a dedicated iPhone developer, who can make sure that you are happy & satisfied with our work.
Look forward to hearing from you and talking to you further thru' Freelancer message board.
Regards,
YK
LEADconcept