What you do mean when you type "marketing"? Are you refering to advertising and promotion only; or are you refer to marketing positioning and strategies; or are you looking at branding?; or are you doing marketing research? ...

It also depends what are you selling, do you already have ready to buy customer, are you able to influence public already, your business model, your product's nature, do you have backer, etc

Different sets of answers above will give you different marketing costs .... so, pls try to answer the above questions