Typically, the prices for the daily specials on the chalk board would reflect the typical prices as shown on the menu. So, the price range can be guessed. Howsoever, it is a law that items in grocery stores be labeled with a price (either on the product or the shelf where the product is stocked), so prices should be on the blackboard, I do believe.
However, I would ask the prices of the dishes I might be interested in. When I dine out, I set a budget for myself, including a tip. So, if something is five dollars over my budget, plus my typical 20% tip, that is more than I wanted to spend on that meal. It is also sometimes awkward to ask "how much is the tuna melt special" how much is the "bowl of seafood bisque". But, I would just ask anyway.
Sometimes I do not even look at the special board without prices and order straight from the menu. Sometimes the waitress does recite the specials and their prices, even though the prices are not written on the special board.