You could say "An apple wood stand for Apple Watch™" and it should be fine.
You can't use their logos or trademarks without permission/licensing, but they couldn't do anything for making an accessory out of apple wood and stating such. In this context, it isn't their trademark, but referencing their watch is.
Apple wood is going to be more expensive than others....why pay a premium for something that people may not believe is worth a premium?
Context is everything (ie product name vs description). If the
name of something creates realistic scope for consumers to mistakenly assume that it is made by Apple when it actually isn't, then there is an obvious case for arguing trademark infringement. And let's be honest, some people are
very easily confused. Trademarks exist to protect brands from this.
In this context, my example product name ("Apple wood stand")
would be a problem. A completely different approach (eg name: Hardwood Watch Stand, description: made from American apple wood) wouldn't be problematic.
I doubt that many accessory manufacturers would be keen to risk a potentially misleading use of the word "Apple" / "apple" in any product name. Much easier to use a different wood - walnut and cherry seem to be very popular
Regarding price, when has paying a premium for a luxury product ever been a problem for Apple devotees?