Rein here from Shopify. That is a very subjective question. Launching a Shopify store really depends on your needs as a business/storefront. It can be as quick as installing a theme and adding your products which can be done in a matter of minutes to a few weeks if you want to get very technical and creative with the process.
Are there specific needs you are looking for that I can give you a more specific figure? Can I ask why you are asking this also?