I don't suggest to buy this boxes

[Alcyone46]

I have watched too many videos about this boxes opening and i buyed 14 boxes too but it doesn't worth it guys. I spend about 100.000 GP, i prefer to buy this bag on store it is a better choice cause i already have too many perm bags, i have ghost shark backpack it is better than terrain 2s..............

[OverConfidence]

I already had several weapons permanent in the basic weapon box ^^but I only open that of event I do not buy ,You should open the preniums, you have a chance on two to have a permanent object ^^ 30 days / permanent

[Wariel]

Yeah I feel like you have a higher change on getting perms with a Basic Weapon Mystery Box.
I've gotten several perms from them. Rarely get perms from the Basic Gear Mystery Box.
Note: I've only opened the ones from the events >.<

As OverConfidence suggested, buy the Premiums, they have better items, yeah it'll be more expensive.
But better chance at getting some rares you don't already have than common items.