If you found a qualified tenant to sign a lease with the landlord and the lease amount is for more than you pay, then you should not be penalized for moving out early. Your security deposit would be returned assuming there are no damages, etc. You will not receive more than your security deposit back just because the new tenant pays more though.
This answer is a general interpretation of the law and is not fact specific to your case. Likewise it does not create an attorney-client relationship. You should seek an attorney for a review of your specific facts and documents. My firm is All for the Family Legal Clinic, Inc. a nonprofit public benefit corporation that charges on a sliding scale based on income and family size. For a consultation contact us 510-999-7732 or at our website www.allforthefamilylegalclinic.org