First of all, we're not talking a couple of hundred dollars; it's a couple thousand per month. And that's only if one has one account.
Second, you conveniently forgot to fully quote the TOS. What it says fully: "You acknowledge and agree that a fine up to $2,500.00 USD is presently a reasonable minimum estimate of...damages." Though this is completely hypothetical, if you think that Venmo could not orchestrate its complaint in such a manner as to show damages of $2500.00, I believe you'd be sorely mistaken. Additionally, the words "acknowledge and agree" have a pretty powerful effect in US law.