ATM git-annex has
remote..annex-cost remote..annex-cost-command # command is not provided cmdline options by annex
to set the cost for a given remote. That requires setting up one of those variables per each host, and possibly hardcoding options for the annex-cost-command providing e.g. the remote name.
wouldn't it be more general and thus more flexible to have a repository-wide
which could take options %remote, %file and assessed accordingly per each file upon '--get' request to allow maximal flexibility: e.g. some files might better be fetched from remotes supporting transfer compression, some from the web, etc. Also it might be worth providing %remote_kind ("special" vs "git") to disambiguate %remote's?