I don't think I am more susceptible to the Ikea Effect than the average person. Then again, I don't see much value in built sets, whether I built them or not.
Looking at the experiments that were used to test the Ikea Effect, I do believe that if I was given the option to buy either a pre-built Lego set or one that I built myself, I would slightly over-value the one that I built. However, I would value BOTH of these far lower than an unbuilt set.
I've bought sets at retail price to build them. But if I built it without buying it, and then was asked if I wanted to buy it, I'd probably only be willing to pay 50% or less.