You’re getting hung up on the MSRP which is only 1 of the factors when leasing. Here’s an example of what can be done on an SQ5 in Texas: SQ5 Prestige - Texas (it’s a higher trim, much higher MSRP and has MSDs but the equivalent numbers on a lower MSRP P+ will be close to your GLC300 numbers as they lease better).
A $46k GLC300 is not good value at $650p/m. If that’s the vehicle you want then go for it but in that market segment it’s on the top end price-wise. I’m guessing you’ve looked at the Stelvio and ruled it out? They would be in the $500’s, drive better but interior not as nice.