How to keep the user on the site. Idea.

How to keep the user on the site. Idea:

Situation:
You have a website that presents a free service to users.
You ran an ad campaign (let's say), and a small stream of users reached out to you.
Question:
How to make users stay on your site and visit it often.

Preface:
Tell me how you feel about the item you received for free and how you feel about the item you received for money. Of course the value is quite different.
Suppose you use mail on mail.ru for free, or you use mail on mai2.ru (example) for money, very little money. And so, in mail.ru you along with everyone use it, and everything is in order. But on mail2.ru you got some privileges, additional features, premium access, cool.
The same thing about livejournal.com - everyone uses it for free, but who wants a little more functionality, pays $ 2 a month (funny), it works.
Now the situation is, we sit and drink beer, and I tell them that I’m a ZhZhist ... and then one of the drinking buddies says, "And I am a Premium User." And this is precisely the word Premium, it pulls back in LJ constantly, as it differs in something from others. He DOESN'T forget about LiveJournal, and I - I'm free, I’ve forgot about it in half — forgotten ...

Morality:
Web services should have a commercial side. Any additional features. This makes the user DO NOT forget about your site, and be proud of it. That leads him back to you.
')
Problem:
Everyone is tired of this topic, pay. Moreover, buy from us for a year and get a 10% discount.

We are used to:

1 Month 12 $
3 Months 32 $ (discount 4 $ WOW!)
6 months 60 $ (discount 12 $)
Year $ 120 ($ 24 discount)

And everyone is already tired of it, all these discounts, prices ... the more, the cheaper.

But the user is not being kept, he is being kept for a month, as more is a pity for the money. (But you are sure that your service is the coolest, and that the user will definitely need it for a whole year!)

Let's not forget that our goal is to leave the user on the site, and not get $ from it.
We decided above that the user remembers the project while he is there Premium and is somehow different from the others. OK.
Creative solution:

1 Month 12 $
3 Months 12/3 = 4 $
6 months 12/6 = 2 $
Year 12/12 = 1 $

Yes, yes, it is exactly 1 month, it costs more than 1 year. That's it for this user will pay attention too.
But - a very important point. It is clear that the user will buy a subscription for a year. (Do not forget that we want to leave it on the site, and not get $ from it). Now our user is premium for the whole YEAR and throughout the year, he will receive a Premium newsletter! (Not like everything, but he: Premium) - by itself, the attitude to the mailing will be different.

The final :

Make the user feel Premium all year long!