Rares cap out at around 150LY from the origin
Well, everything about rares (aside from common variables) can be determined from their purchase price (or the galactic average, whichever). If you do all the math (and I don't think it's been published, tbh, although someone did work out a 3-variable solution -- just turns out that all three variables are dependent) it turns out that the more expensive the initial price, the farther you have to travel before the sigmoid function starts to level out.
As an example, disoma corn (cheap) hits its middle point (half the potential profit) at less than 100 ly, whereas ridley scott leathery eggs hit middle point at somewhere around 160 ly. To reach the part where the latter really flattens, you have to go out to around 200 ly.
But you are entirely correct in that rares do have a cap that is approached asymptotically and so trucking rares halfway across the galaxy makes little sense from a profit perspective.
EDITED to add the details, since I might as well get it posted somewhere. It haven't looked at this in pretty much exactly a year, so Frontier could have changed any number of things related to rares and I wouldn't be the wiser.
The 3-variable solution, price based on three variables in addition to distance, was found by someone else maybe 18 months ago (it's worth noting that there are incorrect versions of this formula around). I believe the user to first uncover the formula is "p2k" (
here).
Selling Price by distance (x):
SP(x) = p0 + p1 / ( 1.0 + exp( - ( p2 * ( x – p3 ) ) ) )
Well, if you gather a whole bunch of data and juggle the numbers a fair bit, it turns out that p0, p1, p2, and p3 are not independent variables, except for p2 (which is a constant). In fact, they can all be calculated from p0, which is the base purchase price.
p1 = p0 * 0.4 + 15795
p3 = p0 * 0.002 + 99
p2 = 0.0677
Okay, so there it is. Trusting stuff I jotted down a year ago and barely remember. And sorry for the OT
