Schwalbe are probably the biggest name in cycling wheels and tyres and inner tubes and for good reason. They are always of top quality and their prices are more than fair.
Buying in bulk is a great way to save money on an item that you'll know you'll get loads of use out of. Make sure you've used it before though before committing to buying a bulk amount.
We don't know too much about this cheap inner tube. The reviews coming back are pretty good though, and like we said, this is one cheap inner tube. That's due to the 70% off price at Ribble Cycles right now.