How do online bike shops make any money?

I just bought a few things from Wiggle: a new bike light, the Holy Hand Grenade of Antioche and a reflective rucsac cover.

* The lights were cheaper than buying the separately as they were in a combi pack.
* All three items were listed for lower than the RRP.
* There's an extra 20% off lights in November.
* There's an extra 10% off all orders over £50 in November.
* P&P was free.
* I got a fiver off my order with an e-voucher that they'd sent me because I'd not bought from them for a while.
* Hamsterley Trailblazers get 10% of the order, because I used their affiliates link to go to the shop.

How the hell do Wiggle make any money?

Update: Everything arrived this morning, with a free pack of Haribo jelly sweets. The lights are bloody bright!