I still don't understand how DG bid $0.50 and it went to $2.44. Something isn't right there. According to how it's supposed to work, his maximum bid should have been $1 if Dynamic up and down was on, or am I missing something?
From the AMS page:
Dynamic bids - down only
When you choose the "dynamic bids - down only" strategy, Amazon will reduce your bids in real time for clicks that may be less likely to convert to a sale. Any campaigns created before April 2019 used this strategy.
Suppose you're advertising a book, and you bid $1.00 for the keyword "thriller." If Amazon sees an opportunity where we predict your ad may be less likely to convert to a sale (e.g., a less relevant search query, on a placement that does not perform well, etc.), we might lower your bid to $0.20 for that auction.
Dynamic bids - up and down
When you choose the "dynamic bids - up and down" strategy, Amazon will increase your bids in real time for clicks that may be more likely to convert to a sale, and reduce them for clicks that may be less likely to convert to a sale. We won't increase your bids by more than 100% for placements at the top of the first page of search results, or by more than 50% for all other placements. Because this strategy adjusts your bid up and down in proportion to likelihood of a conversion, it may deliver more conversions for your ad spend compared to the other two strategies.
Suppose you're advertising a book, and you bid $1.00 for the keyword "thriller." If Amazon finds an opportunity where your ad may be more likely to convert to a sale (e.g. your ad appearing for a highly relevant search query, on a placement that performs well, etc.), it might set your bid to $1.40 for that auction. If Amazon finds another opportunity that looks less likely to convert to a sale, we might lower your bid to $0.20 for that auction.
Amazon can currently adjust your bid of $1.00 up to a maximum of $2.00 for opportunities on top of the first page of search results, and up to $1.50 for opportunities on all other placements.
Fixed bids
When you choose the "fixed bids" strategy, Amazon will use your exact bid for all opportunities and will not adjust your bids based on likelihood of a conversion. Compared to dynamic bidding strategies, you're likely to get more impressions, but fewer conversions for your ad spend with this strategy.
Edit: a little formatting to make it easier to read I hope