A useful budget comparison ends at the hotel entrance, not at a transport terminal or a famous district sign. Add the fares for everyone travelling, any onward ride and the practical effort of moving the bags. Then compare that total with one direct car for the same party and endpoint. A solo traveller with a backpack may have a very different answer from a family with several cases, even when both are staying in the same area.
This matters on Phú Quốc because broad destination names hide substantial differences. Grand World is not every Bãi Dài resort or Gành Dầu village property. A bus serving an InterContinental corridor does not establish a direct ride to every southern resort, Sunset Town or Khem. Central Long Beach also contains different hotel entrances rather than one drop-off for the whole coast. Use the actual booking address and a stop you can realistically use. If the last stage requires a car anyway, include it before declaring the bus the winner. The calculation should not punish someone for choosing convenience: one shared car can be an economical group decision. Equally, a well-matched bus can preserve money for the holiday when the route, bags and arrival time fit. The point is to compare complete journeys, not defend one transport type in advance.