[jventura]

In these kind of things I usually start by multiplying (or dividing) the parameters to get a score (weight=1). Then I sort them, see if they look "good" and add weights as needed. My thinking is that the first result should match my preferences and the last result should not. I know it's a kind of confirmation bias, but..

When I bought my car years ago, I had some parameters, but comparing the price was harder because of devaluation. I remember that I assumed a 15% yearly devaluation so that I could compare prices. For instance, a 2000's car valued 1000€ was almost similar in price to a 1999's car valued 850€..

I make sure to always include a "Preference" (aka bias) parameter and give it more or less weight the more it harms my results.