Create a price list and incorporate a customer discount scheme into it

This is a reasonably complicated project. I have a canvas printing business in Australia that I have an existing price list/chart for, based on specific parameters. I want to introduce new products to my menu, and have a new dynamic price list created for my WordPress website. That means when the customer makes or changes his selection for his print, the job you have to do is ensure that the price displayed changes in line with: (A) the customer request, and (B) to ensure the level of profit I receive is consistent. The profit level is already determined in the existing price list, and after you start work I will discuss these details with you, and the costs involved to me. (As mentioned earlier, this price list is limited to only 2 variables at the moment - 1 style of canvas, and 1 style of frame). In future I will be adding several types of canvas and a few more frames, all of which cost me different amounts. The price list will also need to calculate the cost of shipping to the customer, depending on the size, weight, and destination of the product, but that should be created as a matrix, for the different geographical areas of Australia. Lastly, I want a feature that calculates a discount for returning customers, and also an area for registered customers (wholesale, retail, or professional) to login. I will also want a feature to allow me to change my prices when the price of my stock changes, or when I want to have Sales or offer Specials. If this can be completed either as a macro-driven excel spreadsheet, or as a database, and be compatible with a WordPress plugin for my website and with a Shopify store, that is my preference. PLEASE READ THIS: My budget for this job is AUD$50 - $75 max. Please do not submit applications above this amount. Please contact me for any details and if you have any questions.