"hundreds of billions of dollars"
Germany received $14B (in 2020 $). Most of the money was loans and Germany made the last debt payment in 1971.
The Marshall plan had three goals: 1.) Start the US peace time economy and help transition companies from wartime production to consumer goods 2.) Prevent communist influence in Europe by preventing starving Europeans 3.) Open European markets to US companies by reducing barriers and regulations.
"The Marshall Plan aid was mostly used for the purchase of goods from the United States." --Wikipedia
"Its role in the rapid recovery has been debated. The Marshall Plan's accounting reflects that aid accounted for about 3% of the combined national income of the recipient countries between 1948 and 1951, which means an increase in GDP growth of less than half a percent." --Wikipedia
While the USA might sometimes to present it as a selfless act it wasn't selfless at all. It was what allowed them to become the most powerful country in the word, at least for a view years.
Lastly Trump didn't just want to buy right on the potential vaccines he wanted to get exclusive rights. It was never even a question before that if the EU finds a vaccine then the USA will get it, too. But now he did an action which completely destroy the trust between the EU and the USA when it comes to fighting this pandemic together.