Is it possible that Kubota uses more than one manufacturer for their boxes? The ones I've seen definately had 1/4" end plates, a strap hitch, pull pin scarifiers and was overall a very light weight unit. So light, in fact I don't think Gannon (who by the way builds great stuff) even has a model that light. Or is it possible that some orange dealers are repainting and relabelling equipment with Kubota's name?
Most manufacturers have several levels of boxes. The reasoning is simple. The number of light box blades sold vs the number of really nice units with the features you mention is about 250 to 1. When a manufacturer comes up with a great product, even if it is far superior to everything else on the market, and goes to dealers with that product, the first thing they are told is always the same. "That's a nice product, but the light unit is what my customers buy. What do you have to compete with that?"
Therein lies the problem. Does the manufacturer develop a line of superior products which dealers will not buy because there is not enough perceived market? Or, do they develop a line of value equipment to generate sales and then develop the better mousetrap once they have the dealers' attention?
It's not really the dealers' fault. They have to buy and stock the items that turn their inventory dollars. There are currently over 100 three-point implement manufacturers in the US and several imports. On the one hand, this creates a very competitive martket which is normally good for consumers. On the other hand, it is very difficult for an innovative design to get to market because there is so much "me too" product design that "anything different must be bad" or all these others would do it too.
As to the quality question, if we quantify good quality as 5/8" end plates, hydraulically actuated scarifiers, and a heavy welded hitch, then we have just eliminated most sub-compact owners from ever owning a good box blade by virtue of lift capacity and traction, let alone cost. I think a better way to look at it is to find the product which fits the power unit to which it will be attached, be that lawn mower or 300HP Cat 3 tractor, and which performs the intended use be that smooting gravel drives or building lakes. Don't buy the product for smoothing gravel and try to clear a woods lot with it. You will not be a happy customer.