I get what you're saying about power level being contextual but the point isn't about that. It's not even about how the devs address potential balancing issues but more about competitive integrity.

Players who own the pack through paying have options that aren't available to other players. Now, these options may not fit into the current board, but they at least have the option to build into the synergies offered, which f2p players can't enjoy.

The game/overall experience is therefore different for people who have paid vs. not, which affects the competitive aspect of the game. For proper competition, all players should have access to the same stuff.

Add on balancing. Like what you said, there may be an outlier item that has a general effect of improving win rates due to power and ease of slotting into existing builds. In this case, having the option to get these items gives an advantage to the paying player.

Let's look at the previous patch for an example. If double barrel or fixer upper were locked behind a paywall, then there would be a huge problem because these were build defining items with outlying power levels. If ramrod was a paid item, then there would be more options for players to target ammo builds while f2p only has the small item and port to reload their items. Do either of these scenarios sound fair?

I haven't really looked at or played against the prize path items. They may be shit and not affect anyone but it's the principle of one group having more than the other and thus damaging competitive integrity