Develop a payment component for Joomla component, Mostes Tree

I am looking for someone to develop a payment system for a Joomla Extension called Mosets Tree. This extension must be editable within Joomla 3.2.2 so would need to be a custom built component that work seamlessly with all Joomla upgrades and easily managed by the client. The website is a farm dog selling directory. Each dog is added by the seller from the front end of the website he or she adds information about the dog to a particular category and information about the dog. Then pays for a 60 day run on the directory. This is where I need your assistance. At the moment I have a payment component but it is not suitable it is called "Payments" . My client would like it set up Pricing: Dogs under $1,000 - $20 listing Dogs over $1,000 - $50 listing litter of pups - $30 listing All listings run for a duration of 60 days then they expire if they haven't already removed it. I need to extension developed so if a user adds a dog listing for $3000 he doesn't pay only $20? So what I need is when they put the asking price into the form region it automatically dictates the price bracket they are charged. then from there they have a payment button. Payment Primary payment system must be PayPal. But would like to have Payment Express New Zealand as a secondary. My client wished to use this at a later stage when the website kicks off. Please no time wasters this project has already way behind on schedule. So would appreciate professional developers that know what to do. There could be heaps of work for the right applicant.