The stat upgrading system is a bit complicated, and more so than any other element in the game there are times when in makes total sense to upgrade and other times where it doesn't. You are correct that when players retire you lose the purchased stats, and the cost of stat upgrades are related to the number of prior stat upgrades across the board. In that way it behaves a little bit like a salary cap system, where if you disproportionately boost the stats of one player, you'll be a bit behind the curve when they retire. In general, stat upgrades aren't required to stay competitive, so I personally only spend money on them when the benefits of the upgrade are significantly higher than the benefits of a regular level upgrade. The good news is that even if you blow all your cash on stat upgrades early on, you'll still be able to catch back up to the curve without a ton of extra grind. There's nothing you can do to yourself in this game that isn't recoverable.
New team I'm in the top 10 on the leaderboards for everything besides losses, my team invite code is XUREK679
What does the +500 for 1st mean on team medals leaderboard ?? My team is number one but I don't get what that means.
