This is a fun project. I will add that there is another piece which is missing from this formula, and it will be a variable to subtract from the existing formula. I offer something like this:
S = (c1 x E + c2 x dC + c3 x dT + c4 x L + c5 x SOP) - OC

So I have added parentheses around the entire original formula and subtract this OC from it. OC is the opportunity cost - what value does holding onto this watch have on the state of your collection?

This could be particularly impactful to someone whose funds are more restricted than many in this group. Also someone who has a sought-after watch. No, I am not considering selling my Siffert and I do enjoy wearing it so it already has a nice "S" value. But sometimes I think of how my collection could actually become a collection if I simply exchanged it for a few of the watches on my list.

Maybe I am wrong and this should be a new formula replacing S with CS where CS is the total satisfaction with your collection.

PS - what kind of geeks are we? :-)

: I am posting the following message for Gianluca (as there were
: technical problems with his submission) . . . perhaps his
: formula crashed the server?

: Jeff

: ++++++++++++++++++++++++++++++

: Hi all,

: Today I was speaking with a colleague (an electronic engineer
: graduated at Politecnico of Milan) who was telling me about a
: course he attended some years ago about non-linear systems.

: His teacher explained, during this course, that many systems in
: life can be modelled as non-linear systems, and also
: non-physical things (as happiness or satisfaction, a love story,
: and so on) can be roughly modelled in such a way.

: To make an example, in some circumstances the happiness (given by a
: reached goal, for example) could be seen roughly as the
: derivative (positive or negative) of what you've got (could be a
: new purchase, an increment of salary, a success in your job or
: private life, a new girlfriend, and so on), and tends to a sort
: of “saturation” when you cannot get anymore…

: Let’s make an example: if you win a big amount of money and could
: finally buy the car / watch of your dreams you will have, in a
: short time, an explosion of happiness, the opposite if you lose
: such a thing in a short time or suddenly (lose the job, car
: stolen, wife escaped – OMG, in this case sometimes the
: derivative is still positive  ). When you can have always
: more and more the derivative tends to be saturated (that is
: flat) and you will arrive at a point that you cannot get any
: satisfaction anymore (this happens, for example, also with
: assumption of drugs, alcohol, and so on).

: So the secret to have an happy life seems to be, at this point,
: trying to have a positive, constant – or with low oscillations
: - but not so high derivative in what you can get from your life,
: not big peaks (that sometimes can be followed by big negative
: ones) but neither flat (= constant) rate (that is the death of
: desire).

: This makes me think that you can probably model mathematically the
: satisfaction in collecting (that for me is wearing) vintage
: watches (I know what you are thinking: “who is his
: pusher?”):

: S = c1 x E + c2 x dC + c3 x dT + c4 x L + c5 x SOP
: Where:

: S = satisfaction in getting (or, better, wearing) a vintage
: watch;

: E = Exclusivity (thus depending on rarity of the watch,
: difficulties in having discovered it, and so on);

: dC = delta cost (that is not the cost itself, but the
: difference between what the watch actually worth and what you
: paid for it), so if dC