This is charged by overseas bank as a financing cost. Normally it is quoted as say 3M L + 250 bps, where 3M is 3 Month, L is LIBOR and bps is Basis Points (a unit that is equal to 1/100th of 1%).
To put it simply: 3M L + 2.50%. One should also check on what tenure LIBOR is used, as depending on tenure LIBOR will change. For example as at Jan end 2019, 3 months LIBOR is 2.75% p.a. and 6 months LIBOR is 2.83% p.a
For Issuing SBLC: Importer's bank will charge this cost for Issuing SBLC & SWIFT charges.