Could there really be any variables in this?
The final cost depends on many dactors. Nevertheless, the approximate cost you can calculate here itechcraft.com/app-cost-calculator .
Depends on the client and the theme design, nobody can tell you the exact price. Normally I would charge minimum $1500 for that.
Also, custom theme design is a very tough job and lengthy task that's why eCom owners and agencies now prefer Shopify because it is very easy to use and you don't need to worry about hosting and server security issues like WooCommerce .
Denny Trebbin
Lead Fullstack Developer. Experimenting with bleeding-edge tech. Irregularly DJ. Hobby drone pilot. Amateur photographer.
I can't answer such question for my own projects, how can I do for foreign projects?
But I know a website, which helps answering such questions :-)
http://howmuchtomakeanapp.com/