For a concrete quantitative estimate of the economic benefit (technically, consumer surplus), albeit outdated, probably too low, and not peer-reviewed, see https://meta.wikimedia.org/wiki/Research:Newsletter/2013/March#Estimate_for_economic_benefit_of_Wikipedia:_.2450_million_by_2006_already (The Economist cited the aforementioned Shane Greenstein, who "thinks Wikipedia accounted for up to $50m of that surplus" as of 2006 - in other words, Wikipedia provides a good that otherwise people would be willing to buy, spending $50m on it that instead they get to spend on something else.)

Tangentially, the methodology of this research is also interesting, as it tried to put price tags on the benefit provided by a small, specific slice of Wikipedia content (images of bestseller authors on enwiki):
https://meta.wikimedia.org/wiki/Research:Newsletter/2015/April#Excessive_copyright_terms_proven_to_be_a_cost_for_society.2C_via_English_Wikipedia_images