Help with a Tiered Pricing Calculator?

Actually have revised formula and spreadsheet. Apologies to Kersplash - I get the same numbers now (but I do have a shorted formula if you wish to use it)

=SUMPRODUCT(B2:B10,IF($A$3:$A$11<=E2,$A$3:$A$11-$A$2:$A$10,IF(E2-$A$2:$A$10<0,0,1+E2-$A$2:$A$10)))

Entered as an array formula

And by the way - Welcome to the forum