Upgrading your cake

So, I told FH that if there's one thing I need for this wedding it's that cake from TWOTY. But realistically, I'm not sure if I'm going to be able to afford it.

Does anyone have any ideas of how much more a special design costs (would be on top of the cost that the RH already gave us). I haven't even started doing cake stuff, so TIA to those of you that can give me a ballpark range!

xo