Of course, it will undeniably involve some substantial initial expenditure for opening a cafeteria, but the final result will definitely offset this.

undeniably 由动词 deny（否认）加上否定前缀 un-（表示"不"）构成形容词 undeniable（不可否认的），再加上副词后缀 -ly 构成副词形式。字面意思是"不可否认地"，表示"毫无疑问地、确实地"。