If you're active on this game, you can easily afford upgrades. I make -240m an hour at these stats and only need 850m to upgrade my T4 from level 1 to 2. It takes more time with higher levels and T5, but it's doable.
It's both: if yo want stats fast then spend money, if not thn don't. I hav spent 13 US dollars and I don't regret it. None of m money went for upgrade tho just name change, jetpack, and avatar.