Barcelona's net transfer spending in Guardiola's 4 years was: 41m, 89m, 19m, 13m.
The first year they spent money on a number of players, the only expensive one was Dani Alves at 35m. They did this after losing numerous players: Ronaldinho, Deco, Zambrotta, Oleguer, Edmilson, Thuram.
The second year is the one where they spent a substantial amount of money: on Chygrynskyi, who was a huge flop, on Ibrahimovic, who was a flop for off-the-pitch reasons, and on "Keirrison", a 14m signing that is widely considered to have been some kind of fraud (he never played a game for the club, ever).
The next two seasons their net spend is very low. This is because they can still get decent money for the bigger transfer flops plus sell some players that don't want to be in the team (like Yaya Touré).
Your analytical failure here is that you are trying to act like Guardiola at Barcelona and Guardiola at City were the same thing. They simply weren't.