[Kirby64]

Instant coffee powder has extremely low caffeine vs. other brewing methods.

I'd suggest that most people, if they're drinking '5 cups a day' level, are brewing a pot of filter coffee via a drip machine. At that rate, each 'cup' (defined as 8 fl oz of coffee) should have something like ~100mg of caffeine.

If a 'cup' of coffee is something like a Starbucks Venti (20 fl oz), Starbucks claims it has somewhere between 410-475mg of caffeine. Two of those and you're approaching 1000mg of caffeine alone.