12:27:30.300 - Workspace.SellArea.SellHitbox.Script:4: attempt to index local 'plr' (a nil value)?

For first, you can put the service of players before script.Parent.Touched

and the :GetPlayerFromCharacter(hit.Parent) only get the chracater if hit.Parent is the caracter if not will return nil, you can check if has a humanoid in player and if humanoid exists get character

script.Parent.Touched:Connect(function(hit)
    if hit.Parent:FindFirstChild("Humanoid") then -- Check if humanoid exists on touch, (you can use FindFirstChildOfClass("Humanoid") for check if the humanoid name has changed)
        -- Get character
    end
end)

after this only get player and if player is not nil.

Full script

local pService = game:GetService("Players")

script.Parent.Touched:Connect(function(hit) -- Detect hit
    if hit.Parent:FindFirstChild("Humanoid") then -- Check humanoid
        local plr = pService:GetPlayerFromCharacter(hit.Parent) -- Get the player
        if plr then -- Check if player is not nil
            -- Add money
            plr.leaderstats.Money.Value = plr.leaderstats.Money.Value + plr.templeaderstats.moneyCollected.Value
        end
    end
end)