As was said, if you want to count the pennies alone, by the time you've built the coop and fed them, maybe it's not worth it. 4 is enough to make eggs for a small family.
But if you consider truly fresh organic eggs, work done for you in your vege garden and the enjoyment of keeping hens as having value, then yes - it's worth it. If you manage your chickens around
permaculture principles then they will serve more than just one purpose which helps to balance the
books.
Perhaps you will be setting their run up as a multi-sectioned area like we are building at our house - you can keep the chooks in one small-ish section (eg 6sqm for 4) at a time, so they clear the grass, manure the soil, eat grubs and slugs, turn and
compost the mulch you put down.
Then you put them in section 2 on fresh fodder and plant your vegetable seedlings in the soil of section 1.
Continue rotating so they eat up the finished vege plants and pest insects for you. Along with your kitchen scraps and the fresh greens they get from the garden, you can supplement them with commercial feed in exchange for your eggs.
Voila! Low maintenance
gardening (no weeding or digging) with eggs as a by-product, the
straw or chip you bring in as chook litter becomes a
gardening asset rather than soiled muck to be removed manually. With our new design based on our
experience with hens on our soil, we will be keeping 10 hens rotating on 3 x 15sqm penned garden beds with
shelter and nest boxes. I'm so over weeding, this seems like the sensible solution to me.
Good luck, I cant recommend chickens enough - it's so lovely to have them clucking away happily outside the window and announcing that your breakfast has been laid!