Xfinity doesn't seem to care about retaining customers - so why stay?

I have a promotion on my internet plan that is expiring next month and I've been on the phone with customer service for 38 minutes (At this point) and have gone around in circles. I want to keep my current plan at roughly the same price. My plan is like $100/month with no discounts, and with the promotion I got last year it's been $53/month. I was told once the promo ends it will jump to $113 but they can get it down to $88/month. This is unacceptable. CS has also tried to upsell a mobile line (which would add more to my bill and NOT what I'm trying to do) when all I want is to get a similar promotion and keep my bill between $50-$60/month. I even escalated the call to a manager because I've worked in customer service and understand that the regular reps only have limited options, and even the supervisor said they can't get my bill lower than $78/month. 

I can literally pull up Spectrum's website and get the EXACT same speeds as the plan I'm on with Xfinity for $50/month. Spectrum is constantly hounding me to switch to them and mails promo offers all the time - I've even had reps physically pull into my driveway and try to get me to switch. I believe in customer loyalty (when possible) and have been with Xfinity for 4 YEARS. If they really aren't interested in retaining customers then maybe it is time to go with a company who does seem to want my business. This is absolutely mind boggling.