Why is it so difficult to sell an app in the app store when its a paid app?

Why is it so difficult to sell an app in the app store when its a paid app?

This is not necessarily a technical question, but it's something that
makes me wonder regarding the effort in coding.We code day and night and
learn to design and put in excess hard work, to upload apps, and all we
charge in the app store is a $ or 99 cents. Yet, people complain that they
won't buy it unless it's free. Even your close friends turn their backs on
you saying they don't wanna deal with a paid app. Like seriously? How
would anyone feel if they worked hard for something and they weren't paid.
No one works for free. Even after constant marketing on linkedin,
facebook,twitter and what not, we haven't had luck in getting enough
downloads.What do I do to make people buy our apps. Even after adding
mpoints etc and making it more lucrative no one wants to deal with the
payment of merely a $ , how stingy can people get. Does anyone have a clue
on how I can market the app?Please disregard if you are not going to give
any constructive advice, if you don't feel it's a constructive question
for any reason, move on , you don't have to down vote or act stupid. This
is a genuine question regarding marketing the code.
Any constructive advice on how to improve it or make it better to market
it better?