Wow, I'd say that's actually a pretty good deal. Don't you hate it when you realize you could have saved some money? Then again, you only lost about 5% on the price. Just look at it that way.
EDIT: Why don't they just call it a 5 liter flask? 5000 mL? That's overkill right?
And, I'm absolutely sure my math is wrong. But whatever...
It is just the way things go for me, as soon as I pull the trigger on a purchase I will find it cheaper elsewhere. I am used to it, really 5% is not bad I guess.