Tanya’s Mascara Confusion

For several years now I have always use the same brand of mascara. But yesterday I was at the store and I decided maybe I should try something different. I walked over to the makeup and didn't even know where to begin! Look at how many different ones just ONE brand had! I picked up one and the color was blackest black then I picked up another and it was blacker black. Which one was the darkest? Was it blacker black or blackest black? How different can they actually be? I think it's all the same mascara inside the tube with just different color tubes so you buy your favorite color tube! I also noticed some were $2.99 and some were $22.99. What's the difference other than twenty dollars?