Charles Koch and David Koch, the billionaire industrialists and right-wing mega-donors, stand to save between $1 billion and $1.4 billion in income taxes each year from the tax law passed last month by Republican lawmakers and signed by President Donald Trump, according to a new analysis out Wednesday.

The new report by the Americans for Tax Fairness details how those estimated tax savings would come from a combinations of the Koch's personal liabilities and that of the business empire, Koch Industries. And while based on available financial data, the analysis, the group explained, "does not count how much the brothers might save in taxes on offshore profits or how much their heirs will benefit from weakening the estate tax."

What they do save in annual taxes, ATF argues, should be recognized for what it is: a return on investments made by funneling huge amounts of money to Republican lawmakers voted in favor of the law and outside political groups who lobbied on its behalf. As the group stated:

The Koch groups spent over $20 million promoting the tax bill that ultimately became law, according to a fact sheet they provided to the Wall Street Journal. Their efforts included town halls, door-to-door canvassing, and television ads—not to mention direct lobbying—in favor of the tax cuts. Now that the bill is law, they’ve pledged to spend millions more promoting it to the public in an effort to protect the members of Congress who voted for it.

"That's not a bad return on investment," the group said in a statement. "What's $20 million when you're looking at a billion or more in tax breaks?"

As reporting last week exposed, and ATF also noted, FEC filings show that the Koch Brother's network made a $500,000 contribution to Speaker of the House Paul Ryan (R-Wis.) the day after the Republican's won final passage of the tax bill in December. Given to "Team Ryan"―a joint fundraising committee which benefits Ryan, the National Republican Congressional Committee (NRCC), and a pro-Paul Ryan political action committee―the donation appeared to many as a return on investment.

The Koch brothers pushed hard for tax cuts that will enrich them. They got what they wanted — and then showered Paul Ryan with hundreds of thousands of dollars, per new campaign finance report. https://t.co/cvawAvgWKF — Alex Kotch (@alexkotch) January 20, 2018

On top of the gift to Team Ryan, the Koch's also gave an additional $250,000 directly to the NRCC.

Talking with the International Business Times, Adam Smith, communications director with Every Voice, which advocates for campaign finance reform, said the timing of the large donations certainly made it look like Ryan was being rewarding for "passing this legislation that overwhelmingly benefits the Kochs and billionaires like them."

Read the ATF's full analysis here.