Does anyone know the type of place I can buy prime beef? Will I typically have to go to butcher or could I get it from a super market somewhere? Also, does anyone have an idea of what the price for an 8 oz cut would be?
The price of a cut of meat depends on what cut it is (oyster blade vs fillet, for example) and where in what country you are buying it.
Prime Beef is an American designation for high grade meat. You will have to go to a butcher or high end specialty shop, if you can get it at all, as such quality of meat is generally bought by restaurants and other purchasers in the wholesale markets rather than making it to retail outlets where individuals can purchase. You might be able to get it through whatever Markets are in your area.
The best quality meat I have purchased here in Australia has been from cattle grown by hobby farmer friends and slaughtered on their property to their specifications (so hung for optimum flavour). If I wanted to buy similar meat from commercial suppliers, I would go to a couple of specialty stores in the area who would order it for me if they didn't have any, or I might have to visit the Growers Markets at 3-4am, or one of the local Farmer's Markets and know who I was looking for.
As @Freya points out most beef that is graded as "Prime" is sold into the restaurant industry. But there is a way to get "Prime or Better" that you may wish to consider. I have both raised my own beef and bought from small ranches where they were custom finished. If you are in the US (based on your reference to "Prime") you can contact into local FFA (Future Farmers of America) or 4H groups (Check out the Ag buildings at your state fair) and you can probably find someone who is raising a few head that they might be willing to sell you one of them after they are done showing him. Because these cattle are being raised as show animals as a project they are usually superior to "Prime". If you buy such an animal and take it to a butcher the butcher will probably charge you to have it 'graded' but if you are dealing with a single beef it probably isn't worth the cost to have the meat officially blessed as "Prime", but that is your call.
You will also need to find a butcher who will also slaughter and hang for you. Such a butcher will work with you to custom cut your beef. Depending on the size of your family, you may want to find someone to split a beef with you...but that is a different matter.
Like others have said, Costco is the only place I have seen USDA prime steaks. I just picked some up for $11.99 a pound, here in Phoenix.