Waggin gave me the answer I wanted. I thought I'd seen prices of about $1000 for a full king spring setup including new shocks installed.

It's everyone else who mis-interpreted my original post and started the argument.

Last post from me in this thread.

Variable rate springs come into their own for very low suspension setups - and also for suspensions where very low profile tyres are used - and of course very low suspensions with low profile tyres

King used to offer variable rate rears as standard fit for their low and superlow spring setups - most likely to minimise bottoming without having a too harsh ride. Their current listings don't seem to actually show the "Comfort" option as the standard low and superlow rear option? (it is hashed as an available option).

There's also a message in the fact that King identify their variable rate springs as "Comfort" option (not "Balls out Performance Option") - because that's exactly where they come into their own - don't kid yourself for a moment that variable rate springs are any better than single rate for performance simply because they're variable rate - they'll definitely be less harsh tho (more significant the lower the tyre profile is and lower the suspension is).

Variable rate springs also need to be carefully matched to the shocks - I've discovered first hand that you need to be real careful about using shocks with variable valving AND variable rate springs - I used variable rate King Lows with my Bilsteins initially (both front AND rear) and the result was very nasty. I very quickly put std rate springs all round and she was sweet.

You'll find that JMM's suspension is probably very low? - and that the shocks are indeed very carefully matched to the springs.

Hey, don't take my word for it - King springs are quite good about answering questions - phone or email them and ask - and likewise talk to Jim or Brendan at JMM (unlike other so called Ford performance shops JMM are very good to talk to).