Cumulative Tier Formula using SUMPRODUCT

Thanks for all of this brilliance Glenn Kennedy in this original post, I am new to the forum and hope to borrow some of that brilliance. I have read through and believe my need is closer to ry's post (see link). I am looking for a cumulative total from the tier using sumproduct.

=SUMPRODUCT(--(C9>{0,101,501,1001,1501,2000}),--(C9-{0,101,501,1001,1501,2000}),{100,-25,-25,-25,-10,-6})
C9=Input

I am so close I can taste it thanks to you. I have broken out a manual calculation along with a breakdown of units/cost in each tier to check the formula. Any help is much appreciated!

Please see the image:Attachment 487646

I cannot seem to get my manual calculation to line up with the formula. Please note the calculation and input fields.