Autofill cell with last value known

Hello community.

I need some help to retrieve the last value keyed from an item and autofill the column, the information is in the same table.

EX:

    Quote         | item    | cost
quote n-1        | item a | 100 

quote n-1        | item b | 50

quote n           | item a | 80
quote n           | item c | 20
quote n+1        | item a | last value (quote n)
quote n+1        | item b | last value (quote n-1)
quote n+1        | item c | last value (quote n).

Plan B is create a new column and show the last known value from that item.
Open to ideas.

Thank you