Who ever heard of a bounty hunter that drives a Lamborghini or flies around in a Lear Jet? That goes for pirates, too! Most bounty hunters I've ever seen might have a nice SUV if they've been successful, and when was the last time you saw a pirate in anything other than an old, rusty, fishing boat?
I'd think for role playing purposes, you'd probably want to limit yourself to the Cobra III. But with the game throwing money at you these days, I guess it doesn't make sense, in this FD/ED universe, to just ignore all that cash floating around.
I could say I miss the old days were bounties were low and it was possible to role play as a scruffy bounty hunter, but I think FD always had it screwed up with pirates flying around in luxury attack yachts.