It’s not a bad deal for the market. I would verify that the mf is base and not being marked up for the discount being given. You could also apply msd to lower the overall cost of the lease. My opinion only, if you are comfortable with the payments and it’s the right car go for it
Nothing wrong with a loaner, but you might be on the hook for an extra service (12k x 3 yr + loaner miles) – might push you over 40k miles (I believe BMW is every 10k intervals, not sure how many services they include nowadays). Also might be on the hook for tires/brake towards the end of the lease. It is also a lower trim build for the loaner – make sure it has the features you want (e.g., keyless entry, which was an option when I considered the X3 in 2019). Without looking into the numbers/taxes more, doesn’t seem like a screaming deal, but definitely seems like a fair deal in today’s market…