[CentOS] any reliable HTTPS/SFTP based FTP software on Linux?

I tried Serv-U, Axway SecureTransport and other several software on Linux , Neither one works as expected.

Serv-U is very inexpensive and can create unlimited FTP accounts, but crashes pretty often with unknown reasons.

Axway SecureTransport is a riduculously expensive: about $1K per FTP account! and each FTP account has 2 months cool-down period on between remove old accounts and adding new ones. It is just far too expensive and over kill for regular FTP uses.

Any one has experiences with SFTP/HTTPS based file transfer solutions, open sources or commercial is fine, as long as it is not too expensive.

Thanks.