Changing gigabit plan to the exact same plan and it's almost $40 cheaper. Feels too good to be true but need a sanity check.

NYC-based, been a customer for around 4-5 years now. I was doing some browsing on the site and exploring my options since I was considering adding TV service and noticed when I switched to the 300 mbps plan and then back to gigabit on the "manage your plan" page, it lowered the expected price for my bill by a significant amount. I am trying to reason about why that is - I'm getting the auto-pay twice so I assume it'll go up by $10 in general, but where is that $45 coming from? And the $20 is a promotion for two years I believe.

I tried chatting with support for more information but they were completely unhelpful, want to avoid calling in case there is some issue that could get fixed, but anything else I should look at? I've checked all the links to terms/details I can find and it doesn't seem like I'm locking myself into any long term commitments, but if that $45 goes away then I'd end up paying even more. I haven't gone through and actually clicked "Place Order" yet so maybe it wouldn't work at that point, but I can get to this price every single time.

https://preview.redd.it/vmlefw3939be1.png?width=721&format=png&auto=webp&s=1ff05ae02093138cf80ac3280aa42c05a15de484

https://preview.redd.it/8q2e7abe39be1.png?width=1323&format=png&auto=webp&s=556f4ca5f3fee31a63df387b0344bc45b895066d