Solution : https://service.sap.com/sap/support/notes/338789 (SAP Service marketplace login required)
Key words :
enter application area 'bk', system issues message bk057, enter table t100s, configurable message types, 's' = success message, 'i' = information message, 'a' = termination message, enter message number 057, activity prices exist, issue message bk057
Related Notes :
| 688883 | Confirmation with price 0: Message BK 057 |