It's a common misconception that you get 50% more resources when gathering with Premium Status. But that's not the case; what you actually get is a 50% chance to get double the amount of resources. This chance is called gathering yield and can be further increased by leveling up your gathering masteries, wearing the appropriate gatherer gear or by eating pie while gathering.
That is supremely misleading! I think that it's a common misconception because you've used language that makes it sound like you get a flat 50% bonus to the number of materials gathered. Would definitely recommend changing that language.
what w0lfwood said.
when gathering say 10 times i get 7 times the standard gathering yield, +1 premium, sometimes gathering bonus from gear, food, mastery, and 3 out of 10 i only get the standard yield.
still havent paid attention to how often that happens, still the text line "premium bonus +1" appears far from 50% of the times
The problem is with gathering 1 resource, you cannot gain a half of resource this if there's a single resource in a node it gives you a 50% chance to get additional resource. Which means, at the end of the day, the premium bonus grants you 50% more yield.
Just to clarify and expand on what was already said above, there are three different things that occur when you go to gather a specific node (based on my in-game experience):
You get the "base" amount of that resource, based on the tier of the resource. T3->3x, T4->2x, T5->1x, T6->1x, T7->1x, T8->1x
IF you have premium, you get 50% of the "base" amount of resources as an additional line on the gather. If you are gathering T4, this will always be 1x resource. However, if you are gather T3 (base=3x) this Premium number will vary between 1 and 2, since you cannot gain 1.5x of a resource. The same is true for Tiers5-8, where you will generally get an extra 1x every other gather, on average, leading to a 50% gain in total. Yes, RNG does happen.
If you have anything that gives you additional yield%, such as gathering gear, destiny board unlocks for a particular tier, or food (pies), then you have a chance at what is referred to as a "Gathering Bonus". This provides you with an additional amount of resources equal to the "base" amount of resources for the node. The % chance to get this starts at 0%, and is increased by anything mentioned that increases you yield%. For example, if you have a combined 50% yield bonus then you have a 50% chance to get an 'extra gather' on the node and receive the base amount of resources in addition to #1 and #2 above (you also get the fame associated with that extra gather). If your bonus yield% totals out to MORE than 100% (which is possible with high tier gathering gear + destiny board unlocks + food) then you will ALWAYS get an additional gather and also have a chance at a Second additional gather. Having 10% extra yield does NOT mean that you get 10% more resources per-say, it only means that you get a 10% chance to get a second "base" gather out of whatever resource you are collecting.
This essentially means that the most resources that are potentially possible to get from a T4 node is 7 (2-base, 4-from 2x gathering bonus+1-premium). The lowest amount possible is in fact 1 (just getting base, with no gathering yield proc or premium proc).