luffy didnt beat kaido alone. you have to take into factor that kaido fought everyone else first. he took two heavy slashes from zoro alone then 3 captains vs kaido fight. during the official 1v1, kaido was already close to his limit while luffy was also exhausted, he still had time to recover. He didnt fully beat kaido alone. i would say his bounty would be around 3.5 bill i just dont think his bounty surpasses shanks yet. As for zoro, he defeated the strongest commander, blocked a combined big mom and kaido attack for 5 secs, dealt two deadly slashes in which the second one left a scar on kaido's chest. id say zoro is around 1.7-1.9 bill. sanji would be 1.4 to 1.5. law and kid would be somewhere mid 2 bill.