Think of it this way, ingress traffic leads to stored data, which is paid every month. In essence this is more valuable than egress, which is only paid once.
There is little to gain from that and the storage still needs to be paid. If you want to do this with any significant amount, it’ll take a while to upload and again to delete. So it’ll still cost you and it wouldn’t get you any advantage. This would also only use ingress bandwidth on nodes, which is usually much higher than egress anyway. Because of how distributed these transfers are, you’re not going to saturate those connections to begin with.
So, you’d need massive resources to even come close to slow down the network, it will cost you and you would have to perform this attack using a registered account. The risk is pretty much 0.