Your bounty doesn't reflect your infamy—It's the threat level of threat you pose to the WG. Rayleigh is someone everyone and their mothers knows but I doubt he had a bigger bounty than even Blackbeard, forget about the other Yonko. Similarly, Mihawk could be more famous than Rayleigh, but if he isn't deemed a big threat to the WG, then he wouldn't get a huge bounty.