While Jessica may earn the most your "source" is just a fan blog rather than actual financial numbers. There is no way any regular person can calculate financial worth without actual numbers, at best it's a very vague guess. We don't know worth of the SNSD members: Taeyeon tours and has projects outside music like sponsorships and TV reduce would earn her a significant amount, Yoona is one of the film industry biggest stars and still getting cfs like no one business and so on for every member. Even Hyoyeon who used to get very little activities has toured the DJ scene (which pays a lot with little overhead costs) and promoted Qatar for WC2022, for all we know she could've gotten a huge pay off for that alone.
Regardless who earns more, like I said before money has zero importance on who is a big name in Kpop. Jessica has no impact on Kpop since she obviously isn't active in Korea, she's certainly not anywhere near Taeyeon, Yoona, Suzy etc level even before B&E.
Jessica got paid 8 figures to join Sisters who make waves. Since then she participated in Seaside band, which was so popular it crossed a Billion views and Great dance crew which is currently the second most popular show in China. She has also had various endorsements from fashion brands including Givenchy, Louis Vuitton, Charlette Tilbury and many more.
Also Jessica is blacklisted in Korea so its only natural that she wont be as popular as other members after 2014. She was banned from broadcast so her oppurtunities in Korea is limited. If she wasn't banned she would certainly be more popular. Her solo albums with love, J and Wonderland did well and sold many copies however she wasn't allowed to promote on music shows so she had a disadvantage. Taeyeon, Yoona, and Suzy have support from their companies and agencies but Jessica doesn't have that luxury. Also popularity isn't the only measure of success.