compilers, documentation, etc.
An MSDN subscription alone costs some €1500 a year, Visual Studio costs roughly €700 a year to keep current, etc.
Plus quite likely running several PCs with several operating systems and FS
versions in order to test on multiple platforms.
Not everyone uses pirated copies of their software...
And of course he's spending a LOT of time on it, time he could have spent on things that make money.
Had he rented out his services as a consultant he might make €100-€150 an hour.