'money off' and 'money on' vouchers econ.

[Patricia Holman]

Помогите пожалуйста перевести эти понятия.
(Есть предположение что это система дисконтных скидок и система накопительных скидок)

Встречаются в следующем контексте:

Now, however, companies are trying to automate the process of evaluating individual customers to reduce the time it takes. For instance, supermarkets accumulate evidence of what you're willing to pay by giving you 'discount cards', which are needed to take advantage of sale prices. In return for getting a lower price on certain items, you allow the stores to keep records of what you buy and then in turn offer you coupons for discounts on products. It doesn't work perfectly, because supermarkets can only send 'MONEY OFF ' vouchers, not 'MONEY ON' vouchers. 'MONEY ON' vouchers have never been a success.

и тут:

When technology allows, firms with scarcity power may use highly sophisticated methods to target customers. It's no secret any more that internet retailers such as Amazon can identify each customer by putting a tracing device called a 'cookie' on her computer. Amazon used to tailor their prices based on their records of individual customers. The company really was able to offer 'MONEY ON' vouchers: two customers buying exactly the same product would be offered different prices based on what, if anything, they had previously bought.