Yeah I actually had a dream last night about that very thing. Ran down and tried USD instead. got a different error message.
>> wallet_market_submit_ask xeldal 8000 USD 27.4 BTSX 0
37001 invalid_market: invalid market
{"quote_asset_id":0,"base_asset_id":22}
bitshares chain_database.cpp:2541 bts::blockchain::chain_database::get_market_bids
{"quote_symbol":"BTSX","base_symbol":"USD","limit":1}
bitshares chain_database.cpp:2562 bts::blockchain::chain_database::get_market_bids
{}
bitshares common_api_client.cpp:1475 bts::rpc_stubs::common_api_client::wallet_market_submit_ask
{"command":"wallet_market_submit_ask"}
bitshares cli.cpp:555 bts::cli::detail::cli_impl::execute_command