Loyalty bonus is my guess.
It is sort of standard unfortunately, you get paid for not asking to leave (since players get sign-in bonus with new teams)
The fact that these old worn out players are being rewarded for leading the team into darkness shows the gross ineptitude in managing the salary structure within the club. Liverpool sets an industry wide standard of what prudent financial management should look like.
To add insult to injury, these grandpas continue to play every game, despite lackluster performances, while players like De Jong, who should be occupying Busquets position, get substituted before Busi in every darn fixture. An aging squad, failure upon failure, and yet these Catalan players receive loyalty bonuses into their mid 30s (and beyond?). It is highly irresponsible.
This idea that any type of meritocracy exists within the club is categorically false. Busquets and Xavi are best friends, hence why Busquets always plays without exception. Amigos don?t bench their amigos!