Because new, in-the-box units are so hard to come by today, there isn't a standard rate for sealed PS1 consoles. That said, expect sellers to ask for hundreds or even thousands of dollars for a brand-new PS1.
What is the difference between the original PlayStation and the PS One?
In addition to being smaller than the original model, the PS One also was compatible with a 5-inch LCD screen (see on Amazon) that attached itself directly to the console.