I don't know about all conferences, but in my line of work most conferences cost up to $2000 or even more (for example "late tickets" to a conference I'm attending in June cost $3000). I guess enough people (or rather, employers) consider it valuable enough to pay this price.
Yes, but you'd not be the one buying the tickets, your employer would.
As we know, prices that can be expensed out have a tendency to be considerably larger.