There is a
BountyAmount column in the Data Dump, but for now it is only filled for
VoteTypeId=9 ("BountyClose" event, i.e. when bounty ended) and only if the bounty was awarded to someone (see an example).
Can we also have
BountyAmount column filled for the "BountyStart" event (
VoteTypeId=8) - with the original amount of the bounty when it was started for the question?
This information is public on the SE itself, so I see no reason for it to be excluded from the Data Dump.
p.s.: if this request got implemented (along with Add UserId information for bounty starters and closers), it would be finally possible to create a query for bounty details retrieval from the Data Dump.