One thing about race cars is that they are expensive to maintain, especially if we're talking about the top-of-the-crop customer race cars. GT3 cars need engine revisions every few thousand kilometers. Mercedes for example advertised the SLS AMG GT3 with the relatively high mileage of 10 000 kilometers before needing a 28.000€ rebuild which is a perfectly fine quality/price ratio.
Ten thousand kilomters was just a safe estimate though. To prove how much more mileage is left so squeeze out of the 6.2l V8, AMG partnered with German race team Rowe Racing and over four years didn't rebuild the engine of one of their GT3 SLS. In these four years, the engine completed 28 VLN (Nordschleife Endurance, 4-6 hours), 3 24h of the Ring and 2 ADAC GT Masters sprint races, which equals to an impressive 50 150 kilometers of full throttle racing action without any issues. The engine even powered the car to a sub-8 minute lap earlier this year.
So there you have it, if you need a cost effective 400k GT3 race car, consider the SLS GT3 to be a reasonable choice.