unexpected result with "Extract"

if I run the following query:

with member [Measures].[SOR Cost] as  ([D Services].[Service Unit Price].CurrentMember.membervalue) 
select [Measures].[SOR Cost] on 0, 
 Filter(([D Services].[Service Description].children,[D Services].[Service Unit Price].children),
 [Measures].[SOR Cost]>0)on 1
from [TC Cube]

I got:

I wanted to hide the second column, so I modified the last query and added EXTRACT:

with member [Measures].[SOR Cost] as  ([D Services].[Service Unit Price].CurrentMember.membervalue) 
select [Measures].[SOR Cost] on 0, Extract(existing (Filter(([D Services].[Service Description].children,[D Services].[Service Unit Price].children),
 [Measures].[SOR Cost]>0)),[D Services].[Service Description]) on 1
from [TC Cube]

unfortunately I got:

anybody knows why I'm getting All All All All ...  in the SOR Cost ?!! and how can i fix it ?