Can't say for sure without seeing the lease details(which Rivian doesn't show). But the fact that this Dual has a cheaper price, yet has a higher lease payment than the Tri suggest that the MF, residual%, or both are different between the Dual vs Tri. This is not uncommon in leasing, many other manufacturers have different MF and residual for different trims of the same model vehicle.
I wish Rivian was more transparent with the leasing terms. A statement like “based on 10k mi per year, money factor of 0.xxx, and a residual value of xx%”
I’m in the process of leasing a 2025 RS1 and I asked them for the details on the lease. Apparently for this particular Dual Max Performance the money factor is .0031 with a residual value of $68,572 and a purchase price of $108,800. They should be able to give you this information.