Hello!
It seems like you want an app that merely displays a website. If that is the case, it can be done in a day. I have done more of these sort of apps than I can count. Although I have to warn you that your app might not even make it to the App Store (it actually depends on the Apple reviewer; some have had luck and got their webview apps approved).
However, I would like to stress that we do need more details about the app (design and functionality wise) in order to estimate the cost and time.
Have a great day and I hope to hear from you soon!