If a Lucky egg is added it should be around 5k to buy since how helpful it is But I personally don't think it should be added because that's a good thing for people to sell
Personally, I think Lucky egg's aren't that hard to find - are you guys still having issues finding this item?
I've found 3 so far, traded one for an eevee, and the two Im using for training. I really don't see a purpose to add them, and if they were to be added, way higher than 500 myms