In my area people want egg layers for $5 but most generally I see pullets selling for $10-15 if they are at point of lay or already laying. The problem I see with "already laying" is that it can be difficult to tell how old the hen is, and how much longer you will get eggs reliably from her.
Since we have a lot of people in our area who want egg layers, I buy extra day old sexed chicks at the feed store, raise them to about 6-8 weeks of age, and sell them for $5-7.
I actually worked out the cost of raising a hen to point of lay. If I buy the chick for $2.50 - 3, feed it for 20 weeks, the cost wrks out to around $12. And that doesn't include the initial vitamins/electrolytes, brooder care and electricity for brooder lamp, anything else they eat besides bagged feed, and my time / effort.