You, of course, don't have to do it this way, but doing so will ultimately save time, money and frustration. The objective is to avoid redoing as much as possible. Revision is good, but the later it occurs the more work can be wasted, especially when it comes to web publishing. The work can be reduced by the creation of templates or guides that are used as starting points for each page. It can be reduced to a greater extent by automating the process.
Online commerce is a good candidate for such automation.
When the production and programming is close to completion, the site's pages and programming need to be reviewed and tested. This can be done by turning the site on but only with restricted access. This allows you to see the site as it will appear live so that any editing mistakes or programming bugs can be corrected. This step would be completed by you approving the site to go live. Your site needs to be marketed.