rip someone off: ぼったくる
If someone rips you off, they cheat you by charging too much money for something or by selling you something that is broken or damaged.
Rip off definition and meaning | Collins English Dictionary
The car dealer ripped me off.
the best someone can do: 買い手が支払える最高金額、または売り手が提示できる最低金額。
Is 25,000 yen the best you can do?
his/her last offer: 交渉における売り手、買い手のどうしても譲れない金額。
Is 22,000 yen your last order?
語尾の t と語頭の y の連結
the best you can do -> the / bes-chu / can do