Well, I still go for a variation of Murphey's law,
which I found
to fit at least my experiance:
As soon as you aquired someting you belive to be truly rate and
unique, A second incarnation will popup close thereafter.
And as a bylaw it's stated:
The price asked for the second item is as lower as more you did
spend on the first.
I always refer to it as the Law of Affinity;
I saw it printed in a WWII collectors catalogue in the 80's and it
stuck
Objects have an affinity for each other equivalent to
(5/number you have seen)^(price)
The corrolary runs;
After the first object, all subsequent objects have a maximum price of
(price you last paid/(number you own +1))