It depends on your product niche and how big is your project is and what problem you are solving I mean is your bussiness need more than 10000 customers in order to generate a handsome income (When your profit margin is low ) . or is your product only 100 to 200 customers only per month in order to generate you a good profit plus what is your budget for the marketing of your product which type of audience you are targetting and many more things .
Here are the key things you need to write down first once you get good understanding of these key points you can datermine the needed budget by yourself
1. is your product is of daily use like furniture food etc or is your product niche falls in once in a life time or once in a year use such as ceramic tyles or buidling materials etc
2. what is your targetted audience write everythihg down (their age , online presence , their average budget ) you can get these things by surching on google using your niche keyword
3.what is your budget
4. How many orders you expect per month