Bill now over $300 per month. This can not be normal!! What's happening with Xfinity's pricing?

Hi. We have been loyal customers with no breaks in service since the 1980's. I have Hallmark Plus as my only added subscription. I have an internet that I pay very high costs for each month that downloads at speeds of 25 to up to 34 Mbps. I have been charged for high speed internet for the last several years and that has been and continues to be my rate of speed. What exactly am I paying for that cost so much? Please explain. Thank you.