How much does it cost to integrate with the payment system at the checkout in the store?

Question

Project management

Good evening, unfortunately I am very poorly versed in the subject area and I ask you for help in estimating the cost of developing one element of a large system. I will not describe the general essence of the system, so as not to distract from the essence of the issue.
Case: a user in a supermarket goes to the checkout with purchases and actually buys everything that he put into the grocery basket. He has our application installed on his phone, which is in his pocket.
1) How to determine what kind of person it is at the time of purchase? Perhaps we need to supplement the cashier's equipment with some gadget of our own, for example, a webcam that reads a qr code from a mobile phone. Or is it easier to give a person, along with the application, a card that the cashier will swipe through the reader?
2) How to determine what exactly he bought? How to get from the equipment that is at the checkout a set of goods that he bought?
So, with a slight delay, our server should receive data similar to "Vasya bought milk and bread." You can not trust the user, so that he does not "stumble".
The problem is that the task is set for an abstract set of equipment. Those. the store where the integration will be carried out is not yet known, but the approximate cost of developing the solution should be found out now. I understand that the answer at best can contain the order and currency, but it's better than nothing. Thank you!

Answer 1

I once spent 2 years of my life developing and launching a similar project (a collective loyalty system in the form of a mobile application + integration with systems in institutions)
To be honest, I’m too lazy to write, but if you dial me on Skype dentelis, I’ll tell you with my voice what you have to face and technical side, both in terms of usability and in terms of sales of all this.

Answer 2

How much does it cost to integrate with the payment system at the checkout in the store?

Five - a seven-digit amount in rubles.
Work out the TOR in detail, then it will be possible to talk about the cost of development.
Obviously, the final budget depends on the qualifications and number of specialists, as well as on the time allotted for development.
Easier on the card.
Study the documentation for cash register equipment and cashier's workstation. Options are possible.