When developing a new food product, which are the most important factors? Competitors? Local taste?market needs?cost of production?sales expectations?

Price, Quality, Services.

Evaluate a Business Plan first and work on market study!

According to me, local taste then sales expectations (as it include perchasing power of customer and market study), then calculate your profit means feasibility study (availibity of raw material, transportation cost etc).

Market needs then the sales expectations

The best and Only successful approach is to start your thinking by the customer. getting customer insights, understanding customer behavior and motives is the key for both innovations and renovations.There are many ways to get this information. Everyone look at retail audit data but don't miss going yourself and looking at market.

Get inspiration by looking in different countries cuisine and sometimes there are interesting solutions or products come from other products categories so if you're working in meat, you may find very interesting idea from pastry for example.Finally this is an interesting website for food product development http://www.nzifst.org.nz/creatingnewfoods/