The prize of this king of spices varies in my own country. Black pepper has gained prominence over the years because of its nutritional benefits it has on the body. For this very reason, it made it more available thus accessible to everyone who wants to buy it. Although over here in my country, most people can barely relate with it has peppercorn, but both the sellers and buyers commonly refer to it has black pepper.
You can get them at measurable quantities both grounded and ungrounded. The ungrounded are often in dried form which can be grounded into the grounded powdering form. They can be bought at cheap prizes as they are tied into smaller qualities.
In terms of where they can be bought, you can get them at local markets, as they are readily available in these places unlike online where you have to order for them, which would take longer time for them to be delivered.
I prefer buying then directly from the local market instead of ordering for them online. And I also like to see how they look before buying them.