How to exclude the use of an account on the site by several users?

Question

Startups

The problem is not new, of course... But I managed to find only this one:
www.drupal.ru/node/69747
But there is no clear answer there.
So, there is a site - an aggregator of discounts.
Monetization: paid - got access.
How to make it as difficult as possible to transfer an account like "I paid, you can look under me"?
Registration only through social networks - you can, of course, but!
Firstly, it will exclude the segment of users who do not use them, and there are quite a lot of those. Secondly, you can always create a left social network account, and use it all together.
Maybe someone once solved a similar problem? Surely a whole range of measures is needed here ...
Please share.

Answer 1

It all makes no sense, you know why?
-Hi, I have an X account, come on, I'll buy you what you need, I have a 666% discount
-Oh, nishtyak, buy it!

Answer 2

Does the site receive money only for a one-time user registration?
Register with a phone
And in order to use the discount, a person will have to receive an SMS (and tell its contents to the person who physically provides the discount).
In fact, it's good that the account is being transferred. This means the sundress has begun to work.

Answer 3

OH, yes, like 2 fingers)
1. The average weighting of periodic calls.
2. Average weighting of the number of unique IP addresses (+ subnets) and User-Agent per account for equal periods of time after registration, relative to others.
3. Deviation from the total indicators by more than 2 times - ban. (we prescribe the conditions in the offer in advance!)
Profit!