Why would Comcast rather lose 2 customer accounts rather than charge the same price for the same service?

I have one account that I was able to secure a $50/month for 1 year (not the 5 year for new customers) for 1 gig.  When I tried to change over my other account (located in the SAME city, one mile away) to this same cost, I was told it was not available for that account.  It was then identified that I was asking for something "UNETHICAL".  Apparently, to ask for the same price that new customers and and existing customer was offered is UNETHICAL?  For some reason, Comcast thinks that it makes sense that for one of my accounts to pay more money for a slower service is a "deal".  I need help to understand all of this.  I am only asking to be treated the same as other customers.