Thank you very much, Xoria. And yes, what I didn't specify in my reasoning is that I used Marne as a reference for the rate of income and calculated the price from that, having what you said in mind, that Marne is the center of exodus.
However I checked the rest of the stations based on FLStat and FLCompanion, and the most differences I found are Lapalisse with +0,136, Vichy with +0,142 and Grenoble with +0,157 cr/sec/slot in favor of Houston, these however result only in 2,058, 2,017 and 2,016 cr/sec/slot Fugitive routes, not the most profitable trade routes around. The best one is still Burgundy's Macon with 2,652 for Pittsburgh and 2,626 for Houston.
Althought I understand the possible flaws with the above calculations, such as not having access to the new maps we'll get with the update, but if these obstacles would disappear, so would my flaws and I could conduct math more precisely.