Is there usually a performance impact between localhost XAMPP and hosting server online?

For Instance:

I have a website that has a form of category checkboxes that adjust a resulting array of .gif img src paths. and in XAMPP localhost, it runs PERFECTLY, the script runs flawlessly and there is a function that compares width and height and resizes it to fit browser window and everything.

The Problem:

Then when I upload it on "name.com" Domain Hosting, the script is so slow and images are resized after like 3 seconds of waiting. I figured that was just because its a cheap shared server, so I am now trying Amazon EC2 Beanstalk and it is still kinda slow and laggy.

The Question:

Is this normal? Is there usually a noticeable discrepency between localhost and server performance?

-Thanks