My previous car a '99 Miata was cheap to run but needed tlc in the form of plugging block heater in and constant recharging of the battery. The battery was located in the trunk and exposed to the cold. The C model had the battery in the engine compartment. Also the battery in my 99 was small.
Conversely the Boxster does not need a block heater and the battery is big enough to do the job. However it does not have Japanese durability of many of its parts. Anybody should have eyes wide open before buying a Boxster and be well aware of the costs of running one. The long term quality is not there but the fun factor will always be there.
G.