Indeed. If you track your K series car regularly then a dry sump is a must.
The Apollo does give some benefit on its own, but it simply isn't enough to protect your car once you start going quickly on track.
I'm not 100% sure having been out of the loop for a little while, but I believe Pace's 840GBP (or whatever the shelf price is - and I assume this is +VAT) excludes a tank and any fittings/extras you might need/want. However, if fitting it yourself I'd be surprised if it cost much more than 1200 quid incl. taxes. Which is still a lot less than Caterham's system (the only advantage with which is that it has been proven in a few year's racing, where as the Pace system, as applied to the K, hasn't. Works though).