Joining multiple formulas into one

I've managed to reproduce your results with the following steps

Load the sample data and add a class using a conditional column for Promoters etc .

let
    Source = Excel.Workbook(File.Contents("C:\temp\Sample Data Set.xlsx"), null, true),
    #"Sample Data_Sheet" = Source{[Item="Sample Data",Kind="Sheet"]}[Data],
    #"Promoted Headers" = Table.PromoteHeaders(#"Sample Data_Sheet", [PromoteAllScalars=true]),
    #"Changed Type" = Table.TransformColumnTypes(#"Promoted Headers",{{"likeliness to recommend", Int64.Type}, {"water quality", Int64.Type}, {"water price", Int64.Type}, {"Weights", type number}}),
    #"Added Conditional Column" = Table.AddColumn(#"Changed Type", "Class", each if [likeliness to recommend] = null then "Passive" else if [likeliness to recommend] >= 9 then "Promotors" else if [likeliness to recommend] <= 6 then "Detractors" else "Passive"),
    #"Changed Type1" = Table.TransformColumnTypes(#"Added Conditional Column",{{"Class", type text}})
in
    #"Changed Type1"

Add a new Query for the ratings we want to see. e.g just 0 to 10

let
    Source = List.Generate(()=>10, each _ > -1, each _ - 1),
    #"Converted to Table" = Table.FromList(Source, Splitter.SplitByNothing(), null, null, ExtraValues.Error),
    #"Renamed Columns" = Table.RenameColumns(#"Converted to Table",{{"Column1", "Rating"}}),
    #"Changed Type" = Table.TransformColumnTypes(#"Renamed Columns",{{"Rating", Int64.Type}})
in
    #"Changed Type"

Add 2 relationships for price and quality to the ratings, but disable them both.

Now add measures to calculate the Price and Quality ratings picking the relationship using USERELATIONSHIP

WaterPrice =
 (
    CALCULATE (
        SUM ( 'Sample Data'[Weights] ),
        USERELATIONSHIP ( Ratings[Rating], 'Sample Data'[water price] ),
        FILTER ( 'Sample Data', 'Sample Data'[Class] = "Promotors" )
    )
        - CALCULATE (
            SUM ( 'Sample Data'[Weights] ),
            USERELATIONSHIP ( Ratings[Rating], 'Sample Data'[water price] ),
            FILTER ( 'Sample Data', 'Sample Data'[Class] = "Detractors" )
        )
)
    / CALCULATE (
        SUM ( 'Sample Data'[Weights] ),
        USERELATIONSHIP ( Ratings[Rating], 'Sample Data'[water price] )
    )

WaterQuality =
 (
    CALCULATE (
        SUM ( 'Sample Data'[Weights] ),
        USERELATIONSHIP ( Ratings[Rating], 'Sample Data'[water quality] ),
        FILTER ( 'Sample Data', 'Sample Data'[Class] = "Promotors" )
    )
        - CALCULATE (
            SUM ( 'Sample Data'[Weights] ),
            USERELATIONSHIP ( Ratings[Rating], 'Sample Data'[water quality] ),
            FILTER ( 'Sample Data', 'Sample Data'[Class] = "Detractors" )
        )
)
    / CALCULATE (
        SUM ( 'Sample Data'[Weights] ),
        USERELATIONSHIP ( Ratings[Rating], 'Sample Data'[water quality] )
    )

There are some rows that don't match a rating due to nulls.