It could be because they are beginers and they not only practice on them but they might enjoy making them for fun..??
If you want customers you first have to advertize:
How better to advertize than to either sell really cheap bows or give them away..I mean who can say no to something free right..Some choose to give out freebies with purchase, others free shipping,and most of them super cheap prices..
Well at least thats what i think!?
If i open a Bow store (wich might take centuries) i might do the same at least until i get customers and better yet until i become a tru pro!
OHh and i forgot..Maybe they want to built feedback!..Good Feedback attracks more buyers..