Update on the Exponential term of the transaction cost calculation

[neoofkaia]

Describe the issues and typos
The transaction cost calculation should be phrased as 1e^-9 instead of 1e^9 https://docs.klaytn.com/klaytn/why-klaytn#low-cost

Expected behavior
The calculation should be phrased as 1e^-9

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Additional context
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