Having made these caveats, here are some ways of looking at what it could cost to insure newly eligible immigrants under various assumptions. After the Supreme Court’s Obamacare decision, the CBO estimated that the law would cover an additional 11 million people on Medicaid (at a cost of $643 billion from 2013 through 2022) and 25 million through the exchanges (at a cost of just over $1 trillion over the same period). So, for every additional 1 million people on Medicaid, the federal government will be spending about $58 billion over the next decade and for every 1 million people on the exchange, taxpayers would be spending about $41 billion. Projecting this out for 8 million new beneficiaries would give a range of $328 billion to $464 billion. This would be conservative, however, because the current 10-year CBO estimate includes fiscal year 2013, though the law isn’t going to be implemented until 2014 – thus the actual 10-year cost is understated. Also, this method understates the per capita cost, because I’m dividing for the decade as a whole, even though the population covered by Obamacare grows over time.

As the details of any legislation get fleshed out, let’s hope the CBO provides more clarity on this issue. If there aren’t enough provisions in the legislation to prevent immigration reform from becoming a de facto expansion of Obamacare, my guess is it won’t have that many GOP takers.