Now look at the CBO chart and notice how the steep climb is from what's called the extended alternative fiscal scenario.From the CBO:
After 2022, the extended alternative fiscal scenario also incorporates modifications to several provisions of current law that might be difficult to sustain for a long period. Thus, it includes changes to certain restraints on the growth of spending for Medicare and to indexing provisions that would slow the growth of federal subsidies for health insurance coverage. In addition, the scenario includes unspecified changes in tax law that would keep revenues constant as a share of GDP after 2022, and it incorporates the assumption that spending for programs other than Social Security and the major federal health care programs will generally represent a stable share of GDP in most years after 2022, as it has in recent decades.
But there's a follow up note from the CBO. (bolding mine)
The amounts of revenues and spending to be used in these calculations for 2012 through 2022 were provided by Chairman Ryan and his staff. The amounts for 2023 through 2050 were calculated by CBO on the basis of growth rates, percentages of gross domestic product (GDP), or other formulas specified by Chairman Ryan and his staff. For all years, the Chairman specified that there would be no spending for subsidies to purchase health insurance through new exchanges established under the Affordable Care Act.
You can make a case for anything if you control all the variables.