That's not quite accurate. Willingness to Pay indicates the true preferences of people who have money. If you try to take it as a metric of the preferences of society you will get the preferences of individuals weighted by their net worth.
Fudging the distinction is a fantastically pernicious way to sneak the "capitalism is enlightened altruism" assumption into your argument.
You forget that the market responds to the total volume of buyers at various levels. There are a lot more people in the 0-150k bracket than the people in the 150k+ bracket and when you count the total spending in dollars by each category as a whole, the first group is significantly more powerful.
The most successful companies sell to the masses (McDonald's, Walmart, Google, Facebook). The rich have a much smaller influence on the market than you would like to think.
The preferences of rich _individuals_ have a much higher influence than those of poor individuals.