Looping through a table in an m function

So given the edits to your question I would do this in two steps, first doing an add column to produce the row by row operation where you subtract 1000 from the year and multiply the price by 2. Then do a List.Accumulate over that column adding line breaks between each row.

eg

let
    Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("i45WMjIwMFDSUTI1VYrVAfMMQTxzGM8IxDNQio0FAA==", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type text) meta [Serialized.Text = true]) in type table [Year = _t, Price = _t]),
    #"Changed Type" = Table.TransformColumnTypes(Source,{{"Year", Int64.Type}, {"Price", Int64.Type}}),
    #"Added Custom" = Table.AddColumn(#"Changed Type", "Custom", each Number.ToText([Year] - 1000) & "," & Number.ToText( [Price]*2)),
    Custom = #"Added Custom"[Custom],
    result = List.Accumulate(Custom, "", (state, current) => state & current & "#(cr)#(lf)"  )
in
    result

PS. The Binary.FromText in the first line is just the pasted data from your question