Maybe, if the attacker didn't bother to hack into the WAF itself (generally a softer target than whatever's behind it) and if you bothered keeping or understanding the logs (extremely unlikely to be a good use of resources).
You don't need to understand the logs at the time you gather them for this, you just need to keep them long enough to cover the breach, and to be able to understand them after the fact. Hardly seems like an obvious waste to me, and well worth $500/mo.