"The Law of Diminishing Returns"???

As an economist i would say that first you would need do is to derive your personal production function. Where the thing being produced is good sound which can then be translated into utitity or personal happiness. this would be a weighted function with some variables or maybe in this case just one variable, cost. thus making good sound a function of cost, this is assuming that all components have the same cost to quality of sound ratio. if the sum of the weights of the function is greater than one, then you are experiencing incresing returns to cost. if the = to 1 then constant returns to cost, if less than one diminshing returns to cost. Here are some interesting links to items of interest
http://cepa.newschool.edu/het/essays/product/returns.htm
http://william-king.www.drexel.edu/top/prin/txt/Cost/cost17.html