So to my thinking $300/month for 36 months with $2,500 down is really $369/month. The offer that you quoted seems consistent with the lease payment on a $27k car with $2,500 down according to the TrueCar Car Lease Calculator (see screenshot below).
If I put $46k MSRP and $0 down into that calculator I get $661/month so B&S is either a really good negotiator or BS
... just kidding... I do believe him but suspect his may be some special situation of some sort.
I have no idea how you can figure out a lease payment without knowing the actual details. Calculating a lease payment is not just plug in MSRP, a money factor and done. You are leaving out the most important details, the reduction to capitalized cost, also known as dealer discount and incentives (manufacturer rebates and discounts, special program discounts and dealer discounts). Think of it this way, every $1k in incentives is $27 savings on the payment. $8k in incentives is $220 reduction to the payment.
You also have to know the residual value, that is definitely not a one size fits all and will vary by manufacturer, model and even the type of package. The residual is basically fixed so every dollar discount off of MSRP through capitalized cost reduction is a benefit directly to your payment. And further, manufacturer may sweeten the residual on cars they want to move. The higher the residual the lower your payment. I can say that I feel the residual is higher than I would expect to get for the vehicle at the end of the lease, but I don't care, that's not my risk.
And the dealer may have tax credits they can apply to lower your payment. It's money they either use or lose.
So all that said, that's why I say the only thing I do when leasing is negotiable the payment. I don't care how the dealer structures the deal, they can pull whatever strings they have available.
So anything you just plug into a lease calculator without knowing what incentives there may be is basically the lease payment on full retail price. I'd bet that's what some people pay, but that's just silly as paying retail for a new or used car.
And lastly, money factor is a great unknown. For my last deal the money factor was almost zero. The total "rent" charge, which is basically the finance cost on a traditional loan totalled $15 for 3 years. I guess essentially same as 0% offers if financing.
I don't know if you consider last year of the model to be special situation, but that may have been why vehicle was being discounted to clear inventory. Dunno and honestly don't care, I focus only on payment.
I mentioned this forum earlier, but will share again as information there is invaluable. It's great education on finer points of leasing. You'll also see deals shared by others.
https://forum.leasehackr.com/c/deals-and-tips/6
Anyway, I guess this is now way off topic to the OPs original post, so I'll just let this be my wrap up and let others get back to answering the OPs question.