500-yen taxi; one-coin taxi
A taxi service where rides within a certain area cost a flat 500 yen (one coin). A wasei-eigo term; not used for taxis that simply accept coins.
wasei-eigo (Japanese-coined English), from one-coin taxi
I took a 500-yen taxi home from in front of the station.
In this area, 500-yen taxis are convenient.
Wasei-eigo from English 'one coin' + 'taxi', referring to a flat 500-yen fare.