The eye-popping figure would mean Taylor owns the most lucrative concert tour in U.S. history -- and, in the process, she'd not only be lining her pockets, but also boosting the American economy.

Taylor's multi-billion dollar windfall is an estimate from Peter Cohan, who teaches MBA students at Babson College in Massachusetts. He says he crunched the numbers for The Washington Post, and came out with some astounding figures.

Get a load of this ... Taylor's estimated cut would be larger than the yearly economic output of 42 countries, and a $4.1 billion profit is also enough to send every American a little more than $17.

Swiftee stimulus checks, imagine that!!!

Taylor's making the most of her money from ticket sales and her highly-coveted merch ... while hotels in cities where the "Eras" tour stopped are said to have added $208 million to their coffers, and that's only counting the actual night of the concerts. Realistically, most fans stay at least one extra day.

The economic impact of the "Eras" tour is huge too. For instance, her 6 shows at SoFi Stadium in L.A. injected $320 million into the county's economy, while her Denver shows resulted in a $140 million boost ... and her Kansas City and Cincinnati stops brought in $48 million to each of those cities.

Taylor's sharing the wealth ... as we reported, she dished out over $50 million in total bonuses to her concert crew, and gave every truck driver hauling her tour equipment around the country an extra $100k.