I assume it is not legal to sell products without bill, which Alfa does. The pricing is not lowest at all in the market, and yet we do not get a bill most of the times.
Mobile phones can be bought with bill or without bill, if you buy without bill it is cheaper, and the no-bill rates are written in red on the boards under the phones.
Online stores give better prices and home delivery. You will save atleast 25 to 35 percent if you buy from online stores.