For me personally the cost has been Live 2 (£250) + upgrade to 4 (£120?), upgrade to 5 + Operator (£140) and now the upgrade to 6 will be another £110 ish. I've used and enjoyed each version of course, so I'm getting plenty of value for money.
But compared to (for example) FL Studio with its free upgrades... well, I'm a little jealous of that IMage LIne policy, to say the least! Also I think I'm getting better treatment from Cakewalk in terms of vfm on upgrades and extras.
But there it is - I still love Live
