The underlying of the gas option is BASEFEE - a transaction cost parameter used in the EIP-1559. These options will only be available when EIP-1559 is deployed on Ethereum mainnet. Please note that this may happen somewhere after February 2021 (potentially as late as July 2021 or never).
BASEFEE fluctuates as a result of the supply and demand changes. Supply side is represented by the block gas limit and is set by miners and/or core developers. Demand side is defined by the demand for the storage and computation on Ethereum network (simply speaking - how many transactions users want to execute and the given moment and how valuable they are for them).
While BASEFEE introduces a critical mechanism of fee burning which prevents miners from freely manipulating the gas prices to any value, BASEFEE remains prone to some manipulation from market participants.
a cartel of miners can bring the BASEFEE down
any network users can bring the BASEFEE for short period of times by generating high-paying transactions
For the reasons above we will introduce mechanism protecting the trading from market manipulation but these solutions may end up being inadequate (we will provide the exact calculations showing the cost of attack and the maximum safe trade sizes).
Historical block time chart (see etherscan.io for the current values):