I'm not going to accept gifts
Is there a reason you won't be accepting gifts?
I end up thinking too much about their cost.
It's understandable to not want people to spend too much on you, but its rude not to accept a kind gesture. The gift giver may end up feeling upset that you didn't appreciate their gift.
I think it will bother me if I accept it.
I don't think you should let it bother you, as people are giving you gifts because they care about you. Perhaps tell people that you don't expect gifts and if they do purchase you one to make sure it doesn't cost too much. Hopefully that will help you feel better about accepting them.