This is my code:
(Ends and variables are defined in my script)
if game:GetService("MarketplaceService"):UserOwnsGamePassAsync(player.UserId, id) then player.leaderstats.Money.Value = player.leaderstats.Money.Value + player.CashCollected.Value * .20
if game:GetService("MarketplaceService"):UserOwnsGamePassAsync(player.UserId, id) then player.leaderstats.Money.Value = player.leaderstats.Money.Value + player.CashCollected.Value * 1.2 -- 1 represents 100% of the original value + .2 (the .20 you tried multiplying) adding 20% more based off the players current cash end