My guess is approx. 23 but perhaps others can chime in with their opinion. The center dummy does take up a lot of space so I would imagine you can only fit one row of cupcakes around the perimeter of each layer. If you have more than that you can always place them on the table around the base.
just to get an idea, put some cuppie liners on your drums to figure how many fit. leave enough space in the middle to pretend the cylinders were there.
I ended up snuggly fitting 40 cupcakes (which is how many I needed)
snugly fitting 40 cupcakes, nice work!