There are (at least?) three different ways "ch" can be pronounced in German: Throaty as in "Buch", a slightly altered "sh" sound like in "Bücher", and just as plain "k", like in "Lachs".
I was very surprised to see wiktionaries phonetic transcription and sound sample of "Buch", apparently it is not throaty everywhere.
It's a /k/ in all "-achs", e.g. "Dachs", "wachsen", "Flachs", exactly as in "bochs" the emulator (compare "boxen"), except across boundaries, e.g. "wachsam, wach-sam" (wakeful, at guard), or contractions, e.g. "[Meister seines].Faches/Fachs".
