After they won the CL in 2001:
-R. Kovac from 4th placed Leverkusen, Pizarro from 7th placed Bremen and 2 players from underachieving giants. N. Kovac from HSV and Thiam from Stuttgart...
-2002: Ballack and Ze Roberto from CL finalists and BL runners up Leverkusen. Deisler from 4th placed Hertha
-nothing significant in 2003, just Tobias Rau from 8th placed VW, who became a German international months earlier
-2004: German international Frings from 6th placed Dortmund, Lucio from 3rd placed Leverkusen. Also Hashemian from overachieving 5th placed Bochum, but they aren't a big club.
-2005: Ismael from 3rd placed Bremen, who won a double just 12 months earlier. Also Lahm returned from a loan from 5th placed Stuttgart lol
-2006: van Buyten from 3rd placed HSV. Also Podolski who was a top talent then, but to be fair, they got him from relegated mid tier club Koln
-2007: Klose from 3rd placed Bremen (Bayern finished 4th), Hamit Altintop from 2nd placed Schalke. Not gonna mention transfers from relegation battlers
-2008: Tim Borowski from 2nd place Bremen
-2009: Ivica Olic from 5th placed HSV (6pts behind Bayern), Mario Gomez from 3rd place Stuttgart (3pts behind 2nd place Bayern)
2010: nothing much, just Luiz Gustavo from 11th Hoffenheim
2011: Just Neuer from CL semifinalists and underachieving in the BL Schalke
2012: Dante from 4th place Gladbach, Mandzukic from 8th place VW, some others as well but the clubs weren't any threat by then
2013: Gotze from CL finalists Dortmund
2014: Lewa for free! again from BVB
2015: worth noting they got Kimmich from Leipzig, who weren't a threat yet and not even in BL but were growing into one
2016: Hummels from 2nd place Dortmund, Hojbjerg back from dry loan from 5th place Schalke, lol again
2017: Wagner, Rudy, Sule from 4th placed Hoffenheim, Gnabry from 8th placed Bremen
2018: Goretzka from 2nd place Schalke, free transfer
These are all either historical big clubs in Germany, Dortmund, Schalke, HSV, Bremen, Leverkusen, Stuttgart, or with rich owners like VW or Hoffenheim. Now Redbull owned Leipzig, the contender for the title last few years, isn't safe anymore either
Okay I will make a similar one of Juve starting from 2012 when we started dominating the league:
2012: Asamoah and Isla from Udinese considered big talents of the league. Giovinco from agreement with Parma, most promising player of the league. Lucio from direct rivals Inter on a free. Didn't really dominate the league yet.
2013: Ogbonna from direct city rivals Torino (at the time considerd one of Italys best young CBs), also plenty of shady dealings between Sassuolo with Berardi, Zaza, Peluso and co. Starting time of our B-team Sass.
2014: Only small dealings from smaller teams like Rugani (most promising CB in the league), Sturaro, Marrone, Pereyra loan with option, Romulo loan with option etc. this season.
2015: Dybala (biggest star in the league), Pjanic was the biggest star in Roma. Zaza was signed due to our easy access to Sassuolo. Also Pereyra from Udinese and Hernanes bought from our direct league rivals Inter to help with injuries. Milan loans us Matri in our injury crisis to help win the Coppa for us lmao.
2016: Biggest star in the league Higuain bought from biggest league rival Napoli. Also less significantly Rincon, but also Caldara who was one of the most promising CBs in the league from already well performing Atalanta.
2017: Biggest talent from our most historic rivals Bernardeschi (back then considered as one of the best Italian players in the league), De Sciglio from historic rivals Milan.
2018: Bonucci bought back from Europa league Milan, Perin (best Italian GK in the league after Dollarumma) bought for under market value from Genoa, Caceres loaned from league rivals Lazio to help with injuries. Cancelo came from Inter but they didn't excercise the buy option from Valencia so doesn't really count.
2019: Pellegrini acquired from direct league rivals Roma. Romero bought for way over market price in exchange for shady dealings between several players with Genoa while Sturaro sold the for way over market value due to agreements between Genoa. Demiral acquired for under market value due to agreements between Sassuolo.
2020: Chiesa (one of the most exciting talents in the league) from the most important player of our most historic rivals Fiorentina, Kulusevski (one of the most promising players in the league) from 3rd place Atalanta, Rovella (one of the most promising young mids in Serie A) acquired by paying fee instead of getting on a free due to agreements with Genoa.
I think the talent pool in Serie A has been so bad that we've got a large chunk of our key players abroad, but every single time an exciting player comes around in Serie A he's been ours if we've wanted to. Gabbiadini, Immobile, Berardi, Orsolini and co. have all gone through some kinds of dealings with us over the years even if they never won a spot with us. We kept so many teams on our leashes over the years; now it's Genoa (Pjaca, Sturaro, Portanova, Pellegrini, Perin while we get dibs on Rovella, Romero maybe Scamacca etc.), before it was Sassuolo (Zaza, Peluso, Lirola, Berardi, Marrone, Demiral). To some extent also Udinese and Atalanta had some kinds of dealings with us where we get their creme de la creme and they accept our shit. Teams like Milan and Inter have not had players that we've wanted over the years tbh, but when teams like Roma and Fiorentina do, they act all fussy in the media yet just end up selling cause their finances urge it.