Question about xdai bridge validators and mainnet txns

I was wondering for the xdai bridge validators that send transactions on the ethereum mainnet side of the bridge: where does the ETH necessary to pay for gas for sending bridge validator txns to ethereum mainnet come from? Is this something that the xdai foundation subsidizes? or is there some kind of reward that bridge validators are given that offsets the ETH gas charges for ethereum mainnet? Also, I was wondering how is the gas price for the bridge validator txns to ethereum mainnet set? Is it based off of a gas station, and if so, which setting is it (standard, fast, etc.)?

thanks so much!

they don’t send transactions on the Ethereum side of the bridge.