What makes a speaker thousands more...

What makes, let's say a $7500 speaker more expensive than say a $2500? Is it the drivers, cross overs, cabinet, R&D, all the above, etc...

This could really go towards any componant, like why does Company X's Amp 1 cost thousands more than amp 2? I realize there generally is more power and clarity, but do they really have thousands more into it?