Power Query Replace Data Help Please (Tiime Sensitive)

TobyC84 

Assuming SKU are unique in both tables, you may merge A with B, add custom column for corrected price (if null then oldPrice else newPrice) and do cosmetic

For such sample

generated script is

let
    Source = Table.NestedJoin(
        TableA, {"SKU"},
        Table2, {"SKU"},
        "Table2", JoinKind.LeftOuter
    ),
    #"Expanded Table2" = Table.ExpandTableColumn(
        Source,
        "Table2",
        {"Price"}, {"Price.1"}
    ),
    #"Added Custom" = Table.AddColumn(
        #"Expanded Table2",
        "Price Corrected",
        each
            if [Price.1] = null 
            then [Price] 
            else [Price.1]),
    #"Removed Other Columns" = Table.SelectColumns(
        #"Added Custom",
        {"SKU", "Price Corrected", "V"}
    )
in
    #"Removed Other Columns"