I am not in the field you specify, but, however, I would suggest you communicate with those who have put in proposals with regards to your job posting. All questions you have should be answered correctly by them. Out of that, you would also to be able to gauge who can satisfy your needs best.
A retail website can be built in an hour.
It can also take 100 hours to build a retail website.
Or 1000 hours.
It depends on exactly what you want built, and how much you want it to be customized and unique.
Some people might simply want to use a template or service to allow them to sell a single product. This can be done very quickly and inexpensively.
There are some site owners who will pay $1000 just to have the logo for their retail site designed. Other site owners will pay zero, and simply display their store name using Arial Black in an H1 tag at the top of their site.
Some people might want to craft a unique user experience and build a distinctive, premium website unlike anything else on the web.
You might want to hire two or three different experts to simply talk to for 30 minutes to an hour in order discuss options, before even starting to actually have the website built.
If you really want to save money and time, you should hire multiple developers to work on the same task or project, and then close the contracts on the ones who are slowest or most expensive or turn in work which isn't the best in quality.