I think what some are trying to say is, yes buying a product is slighlty different to buying a service. But at the same time you are still buying a service as well as the product.
You may get chems thats £5-£8 cheaper or a product 30% cheaper, but it may arrive 3-5 days later, when you ring to see where it is or email for help there is no reply or answer for hours or even days. When the item arrives it could be wrong one, damaged or some of the order missing.
OR
Pay £5-8 (or 30% more) and get a much better service, quicker delivery and the items thats you want.
Personaly i dont go on price alone, reccondmendatios count also.
J