The price of a raw, whole chicken can vary from as little as $3.99 to over $20. Yes, the size matters (because usually it's priced by the pound) but the price also depends on how it was raised, where it comes from, and if it's Kosher or not.
The Kosher chickens are always more expensive than the non-Kosher ones (I guess because of the extra work that had to be done)- but did you ever notice they taste better too? I used to think I was imagining it but then I found out it's because...they're all pre-salted! So instead of spending the extra money, salt it yourself:
-unwrap your store bought, raw chicken take out any/all extra innards
-place in a large bowl
-cover completely with water and add at least 1/2 a cup of salt and 1/2 cup sugar
-cover with plastic wrap, place in fridge and let sit for at least 3 hours or up to 24 hours
-when you're ready to cook it, take it out of water, rinse off any salt/sugar that may have not dissolved completely, and prepare as desired (roast, bake, fry, etc).
For the record, I did not discover this technique- it's actually quite trendy these days. Just letting you know that I've done it (actually, I never make a chicken nowadays WITHOUT doing it) and it's not only a cinch but worth every second. Every part of the chicken comes out tender and juicy (even the white meat).