Jesus comforting words

I led a Bible study last night on Luke 11:37-12:12. Jesus words in Luke 12:6-7 reminded me of the 'daily devotions' I used to hear when I listened to the local Christian radio station (I have since repented).

Are not five sparrows sold for two pennies? And not one of them is forgotten before God. Why, even the hairs of your head are all numbered. Fear not; you are of more value than many sparrows.

I can almost hear it now, "And remember when you are down today that you are worth more than many sparrows to God." Of course, gentle Jesus meek and mild would be less likely to utter the words immediately preceding these:

I tell you, my friends, do not fear those who kill the body, and after that have nothing more that they can do. But I will warn you whom to fear: fear him who, after he has killed, has authority to cast into hell. Yes, I tell you, fear him!

   - Luke 12:4-5

"What's the worst they can do? They can only kill you." What comforting words from Jesus.

Now, I would also appreciate help on the sparrow-trade in first century Palestine. Why would you be purchasing a pair of sparrows? Did people keep pets? Surely the nutritional value is not sufficient for them to be a food source. Thoughts?