Basically, yeah. With a €50 set that's clearanced to €20, generally means it's on it's way out and they're not really going to be able to easily find availablity of the set. If someone sees that the RRP is €50 and they're getting it for €40, they think they get a bargain. I'm happy with turning €20 in to €40 and then that €40 might become a Wall-E or Doctor Who as an example.
I can give you a few examples, I bought an Ultra Agents Helicopter for €30, sold it for €55 the next week, RRP €70, or The Lego Movie Rescue Reinforcements, bought it for €30, sold it a few weeks later for €57.50, again RRP was €70.
Means that I keep the cash flow ticking over, so when I find sets which I've marked as planned buys, I have more money to spend.