Depends on the client budget
Things to consider
Domain and hosting price
Content ( product details, pictures and some blog posts)
Custom or shopify/ wordpress ( plugin and theme cost)
Number of revision ( It can be in numbers or time like 2 months)
Your client communication and trust level
Tip from personal experience
Don't forget to give your client all details in starting about what you will do, price of each service and TAT.
Keep the site in your hosting and then migrate aon project completion.