People seem to read past your second question, but yes Luffy's bounty was an equivalent to 30 million Yen. As said in the trivia section of the wiki page on Beli, both the appearance and denomination of the beri closely resembles the Japanese Yen...
In appearance and denomination, the belly closely resembles the Japanese Yen (日本円 Nihon En). The characters Yukichi Skull, Ichiro Kumaguchi, and Hideo Usaguchi portrayed on the belly banknotes are a pun on Hideyo Noguchi, Ichiyō Higuchi and Fukuzawa Yukichi portrayed on the corresponding yen banknotes. "Kuma" and "usa" mean bear and rabbit.
...and so does its value.
Some Images for comparison:
One Piece Beli bills and coins
Real Japanese Yen bills and coins
For reference I put a few prices below gotten from the wiki page. Comparing them to contemporary slave prices or terrorist bounties, it seems that we put more value on human life than in the One Piece universe and have somewhat higher prices going on, but when comparing everyday objects like a cabbage loaf, jacket or brand shirt, it seems that the prices pretty much resemble current Japan prices. Therefore it is safe to say that Oda based the One Piece currency on the currency of his home country Japan.[A reference of Oda confirming this would be nice, but I could not seem to find any]
- One cabbage loaf: 150
- Doskoi Panda brand shirt: 10,000
- Nami's jacket: 28,800
- Human slaves: 500,000+
- Portgas D. Ace's now inactive 550,000,000 bounty