The Spanish set is from the same masters. They all come from Cineteca Bologna. The Spanish set used to be 14 euros. I guess it went up in price after the others were released. The difference in interlacing is because of the way the speed is handled. Most companies use progressive, even though it...
I think the Spanish version is still available at Amazon.es. It's considerably cheaper, but it has no extras. I'm pretty sure it's region free. You might want to look into that one.