Holy Overpriced, Batman! $300?
Anyways... the intake on Defenders is very different from that on the RRC and Discovery, with a 4ft long intake pipe leading back behind the engine to the air filter. The Mass-Air sensor is also at the end of that pipe as well, so you can't just remove it all. You would have to put the filter element where the stock unit is, and that brings up a lot of mounting issues.
If you want better flow, you can just get the replacement K&N element and put it in the stock housing. But the big limiting factor is that long hose, not the filter element. So won't really gain you much.
My oil line fix
My 100k stopped odometer fix
Brace for impact, I'm in a "modifying mood". Massive thread count inbound.