Yeah, I'm up to map 20 and I've gotten 2 cornucopias. I will definitely get some more maps done as I only lost one tank on map 19, but the drop rate seems to be very low, considering we only get seven resets. I see three major problems. First, the basket doesn't have a set amount of them, so you could end up with four for 250 cores while someone else could have to spend 500 cores to get that same amount. Second, the low drop rate and the variable nature of the basket both keep anyone from planning how many cores they will end up needing to spend. Third, this information is vital because with two baskets available per day there are only a total of four to eight cornucopias available for purchase per day. If on the last day you're five cornucopias short and your two available baskets only contain two corns each, you're fucked. And you're also fucked if you spent too many cores on baskets because there's nothing else on which you could spend the corns.
With ghosts/bat wings we knew after the first day how far we'd be able to get each day, and plan our core spending appropriately. But now someone could spend cores and still not get the third copy, and that is a big motivator to actually NOT spend cores. I have no idea why they changed this.