Depends! I know, you don't like that answer but it is the truth. Building a 5-10 page Wordpress website is much different then building a 5000 product e-commerce store. It also depends on the type of functionality you want on the website as well. But to give you an answer for this question, our simple websites at Design ME usually take anytime in between 5-8 weeks to complete IF the client is able to give us what we need in order to do so.
For example, if I need pictures of your products from you, and it takes 5 weeks for you to get them to me....obviously that delays the project.
We have never had a time where we missed the deadline when we had everything and I believe what makes us stand out from everyone else is our process. You will know exactly what is going on, when it is going on and the estimated time of completion of each step we take.