Would you ever buy an ex-rental car?

[konfab]

They're actually not that much more expensive than other cars..

There is a massive misconception that general maintenance on a BMW/Merc/Audi is ridiculous.

The average service on my Merc was about R1500 when I last did it... which was about R150 more than a service on a similar model year Polo or Golf. Yes if something big goes, things get expensive, but that applies to ALL cars these days.

It depends what you are count as ridiculous.
Smaller, more budget cars will always be cheaper in terms of parts cost due to the economy of scale.
For example, the front brake pads for a polo vivo are about R750, whereas on a Merc C200 they are R1330.

It is very dependent on the model of car. As you said, a Golf 7 is roughly in the same ballpark as a BMW or a Merc.

There is a nice breakdown of costs here:
http://www.kinseyreport.co.za/

If you look at the cheap category vs the auto executive category, you will see that there is a massive price difference between the maintenance costs.
For example, a spark plug for a Ford figo costs R60, whilst a spark plug for an Audi A4 costs R290