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Extracting keys from a modern SIM card is very difficult. The cost is way above 10K USD. So a payment card in offline mode is absolutely possible as long as one limits the payments to few hundreds USD.

The bigger challenge is an offline terminal that can easy accumulate tenths of USD in case of a long outage. But then compared with cards the terminal may have better protection.

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What makes it over 10K USD?

In addition to the issue of microchips being inherently difficult to tamper with, smartcards have various hardware and software based anti-tampering measures, that are designed to destroy the chip, if someone attempts to extract the keys from the chip. That kind of security measures are never totally impermeable, but defeating them requires advanced equipment and skilled labour, and the R&D costs of the cracking devices need to be offset, too.

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