Hi there
i think it is a matter of costs and with the new LL pricing it is not reasonable to buy a grandfathered sim for any price.
1 Year costs for a Sim:
1 New Sim: 349$ (incl. 1 month tier) + (11x249$) = 3088$
2 Your Sim: 1200$ (600$+600$) + (12x195$) = 3540$
You see, it is nearly 500$ cheaper to buy a new sim if you hold it only for 1 year
20 month cost of the sim:
1 New Sim: 349$ + (19x249$) = 5080$
2 Your Sim: 1200$ + (20x195$) = 5100$
You see? Your offer is after the 20-th month cheaper than buying a new sim.
The times where sim-owners could ask for 1600$-2200$ (incl. transfer tier) for a grandfathered sim are gone.