I have a hard time imagining that lepin gives two fucks about lego's bag patent, considering they're completely ripping off all their designs. I think it's just too much work for them.
My wife and kids have built the lepin versions of the Creator Chinese Theater, the simpson's Kwik-E-Mart, two big Harry Potter sets, several Lego Batman movie sets, the Ewok Village, and my son built the Death Star in a couple of weeks over the summer. And I have at least 6 more large creator buildings left to go.
Quality-wise... the plastic, fit, and finish are all basically identical to lego. Unless you were looking for the little lego stamp on the bricks, you'd never know the difference. I think out of all the ones we've done so far, we've only had one missing piece. I've had lots of claims from the kids that piece x-y-z is missing, but it never is. It's just that you have to sort through a shit-ton of parts to find the right ones, and it's easy to miss something in the sea of open bags.
The only other issue I've encountered is that on a rare occasion, a few parts aren't the right color. I know on the death star, my son thought there were some missing parts, and he was getting spares from my bins. As it turned out, when he was finished, all the parts were there, but they were light gray instead of the dark grey called out in the instructions. So we didn't know that those were the ones he should have been using, thinking the light grey were used later. The lepin instructions which are basically identical to lego, don't include the parts list like lego. I should have looked at the lego instructions online to see if the light grey were actually used later, but I wasn't thinking that hard about it. A few Kwik-E-Mart grocery bits ended up being random colors different from the instructions, but it made zero difference.
Overall, a few little niggles, but completely worth it to pay 50-75% less, and the final product looks as good as the real deal.
I buy all of mine from Aliexpress, much cheaper than ebay. I've had good luck with both of these stores:
https://lepin02.aliexpress.com/store/2798035?spm=a2g0s.9042311.0.0.TfBYWp
https://www.aliexpress.com/store/2341261?spm=a2g0s.9042311.0.0.TfBYWp
Shipping is free and surprisingly fast (7-10 days). No retail boxes included. It's not an impressive presentation when you open the shipping box (just cardboard or plastic bags full of smaller bags and instructions), but it's all there, and it's dirt cheap.
Now when I go into a store and see retail legos, I just scoff and chuckle. I've ordered lepin sets while standing in a TRU.
EDIT: Looking at the listings, they don't show any of the figures. That's totally weird, as I know the pics and sets had people when I bought mine. So I don't know if they aren't included or if they just can't show them for some lame trademark reason. Very strange.
