They really do make a big difference to the finished look of your socks. Yes they do cost a little bit of money but compared to all the time and effort you have put into knitting them it really isn't very much. If money is tight there are some great tutorials available online to make your own.
If the socks are for you there's absolutely nothing wrong with blocking them in the time honored fashion of bunging them on your feet. But if they are for a gift or, let's face it, if you want to photograph them and Instagram the heck out of them, then sock blockers are your friend.
Whether you choose wooden or plastic or whether you make your own, the blockers allow the stitches to properly relax under just the right amount of tension. Just pop you finished socks in to soak for 20 minutes, blot them dry with a towel, slip them onto the blockers and then leave them to air dry away from direct heat.
Then you can photograph the living daylights out of them.