You may check on your state law to find out whether the state law permits a cooling period for residential leases. As far as I know, it is rare for state laws to have something like that.
A lease is a contract. Once both of you signed and delivered to the other, it is a binding legal document. There are ways to rescind a contract legally without penalty. For example, in California, a residential lease can be rescinded by consent, by mutual mistake, destruction of a property, or by other reasons such as fraud, illegality, or violation of public policy, which makes the initial lease void ab initio. If your reason to rescind the lease is not one of them, then the rescission is a breach of the contract, for which you will be liable for damage.
Generally, if there is no liquidated damage clause in the lease to deal with early termination, then you may have to pay for any incidental damage, consequential damage, maybe attorney fees as well. Whether $2800 is not reasonable is to be determined by a court.
