How many hundreds of thousands (or millions) of your particular 2002 model were made and sold? ...and how much do you pay for your genuine spare parts? My point is that the manufacturer of your 2002 model car is still probably making a tidy profit out of spare parts sales. Indeed, it probably has an entire spare parts division.
How much money is N3V making from the DLS downloads of assets it maintains for older versions of Trainz? That DLS support costs money (servers, hosting, backups, bandwidth, helpdesk, etc) and I somehow doubt that what you pay for an FCT will cover all of that.
Then raise the price of an FCT or build it into the software until you're no longer operating at a loss.