My ISP is a "small" provider that focuses on multi-unit urban residential buildings in the midwest. Their business model is to make an agreement with the building management and provide a baseline service to every unit, while offering upgrades and extra services to individual units that want them. They have an incentive to provide far more capacity than the baseline so they have room to offer upgrades.
I pay $25 per month for 250mb symmetrical and am definitely getting those speeds 24/7. I have the option to upgrade to 1G symmetrical for something like $500 per year, but haven't seen the need.
Unless an ISP is serving a very low density customer base, the cost of building out full capacity just isn't prohibitive anymore. My ISP only has around 20,000 customers and they have direct peering with Netflix, Amazon, Apple and others - clearly an ISP doesn't even have to get very large before those cost benefits arrive.