According to this article, Mercedes' budget was around 470 Euros for this year, and they're the 2nd biggest spender. While it doesn't say where all that money goes (
Though the driver's salaries have been published/speculated), typically the majority of that cash is spent on just the Resarch & Development aspect of the car. I remember hearing that just getting an F1 car up & running is roughly $10 million bucks (which is probably hogwash

), bust when you factor in the development of the aero, the development of the engine & drivetrain, the bespoke parts for the brakes, suspension, body, ect., as well as having the
replacements for these bespoke parts in case they get damaged or destroyed, It's probably very likely that Mercedes, Red Bull & Ferrari are spending more on their cars than Audi spend on the R18.*
*Again, pure speculation. If someone has access to hard numbers, I'd love to see them.
Also, consider that the top Indycar teams spend less than 5% of the top F1 teams.
Christ, I can't spell tonight, lul.