Some of the more expensive brands (Asus, Gigabyte, EVGA) are able to charge more because they have a long history of very good quality and support (although more recently Asus support has gotten pretty bad), as well as a "trusted" name brand.
Some of the cheaper brands (ECS, BioStar, Foxconn, MSI) have had reliability and quality and support issues in the past, so their products are cheaper, to try to lure people to buy them even though they aren't necessarily trusted.
Brands like ASRock are new players to the game, and while they are high quality they don't have the name to back them up yet, so they are cheaper.
You have to remember that Intel is a huge name, known most for their server motherboards, which are *extremely* reliable and well built. They build their desktop boards to the same (or close to it at least ) standards, so they are going to charge more for them.
In answer to your question "Is it safe to..." yes, it is completely safe. No matter what manufacturer you go with, there are very precise certifications that must be held to when a chipset is released, and if a manufacturer can't meet them, then Intel won't license them to use the chipset.
Still, I personally stay as far away from ECS, Biostar and those brands because the manufacturing quality is not as high. Just a personal preference. I am willing to pay a bit more for a better quality product.