Looks like they all work out about the same price, give or take a few pennies. The ESP Stiff Rig appears to be slightly cheaper than the Korda Mouthtrap, but their hooks are slightly more expensive.
The Korda ready mades are actually cheaper than the ESP ones, and the Gardner ready mades are more expensive than both. I'd imagine a bit of shopping around might find better prices for one or the other, but in each case the difference between ready mades and diy is negligible.
So, anyone who struggles to tie these (and they are a pesky little blighter to tie), with a view to saving money, don't bother, the ready mades are good value.