Transforming Columns with specific values

If I understand correctly, you can try the following:

• Use the List.Generate function to generate the basis for your new columns
• After creating the table, with the proper dates and prices in the columns,
  • Transform the Date column into text in the format you specify
  • Set the data types for the Date and Price column appropriately.

let
    Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("NcjBCQAgDAPAXfqW1kSFOIu4/xoW0XveWgZGQ7ASVmyqu2C75L9mNupornGfQf0X6T17Hw==", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [Date = _t, Price = _t]),
    #"Changed Type" = Table.TransformColumnTypes(Source,{{"Date", type date}, {"Price", type number}}),

   newCols=List.Generate(
       ()=>[d=Date.StartOfMonth(DateTime.LocalNow()), p=List.Last(#"Changed Type"[Price]), idx=0],
       each [idx]<Table.RowCount(#"Changed Type"),
       each [d=Date.AddMonths([d],1), p=List.Last(#"Changed Type"[Price]), idx=[idx]+1],
       each {[d],[p]}),

    newTbl = Table.FromRecords(
        List.Transform(newCols, each Record.FromList(_,{"Date","Price"}))),

    #"Date to Text" = Table.TransformColumns(newTbl,
        {"Date", each DateTime.ToText(_,"MM/dd/yyyy")}),
        
    #"Changed Type1" = Table.TransformColumnTypes(#"Date to Text", {
        {"Date", type text},{"Price", Currency.Type}
    })
in
    #"Changed Type1"

Original Table

Results