Banks have a lot of overhead. Typically, they do not write their own software - they buy a package (and spend nearly as much time/money writing integration cod

Banks have a lot of overhead. Typically, they do not write their own software - they buy a package (and spend nearly as much time/money writing integration code, but that's a separate topic.) There's also mandatory costs -- SOX says you must have a disaster recovery plan in place, and you must conduct regular tests. You must have access controls in place, which includes things like mandatory vacation time for sysadmins and developers (so they can't write backdoors into the systems). Customers not having access to their funds because of system problems is highly frowned upon by regulators, so high-availability with redundant computers + software is a given. Passing a SAS-70 audit is just the beginning.