"Pay top dollar" is an informal idiom that means to pay a very high price for something.
For example, you might pay top dollar for a house, entertainment, or a product.
Examples
"Developers are paying top dollar for these houses".
"People are willing to pay top dollar to see this sort of entertainment".
"Our customers are willing to pay top dollar for high quality products".
"If you want the best, you have to pay top dollar".
Usage
"Pay top dollar" is mainly used in the US. It's an informal phrase that's used to describe paying the highest possible price for something.
Related phrases
You can also use "top dollar" as a noun to describe the highest amount that's being paid for something. For example, you might "get top dollar" for your services.