I love resin kits. Some genres don't really need it to pull off a good kit. Take a VF-19, for example. Hasegawa can execute a gorgeous model of it using plastic, because of its general shape and lack of extremely meticulous details (besides the panel lines, which are cake) in 1/72 scale. That's all fine and dandy to me, don't get me wrong. Planes and stuff have general shapes, with large, flat, aerodynamic surfaces.
But some other kit genres are very hard to model accurately in anything but resin in a typical scale (1/100, 1/72), simply because of their design. Kits from the mecha series Five Star Stories are a prime example. They are semi organic; basically robotic, soul-infused animals with armor bolted on to them. The detail inherent in FSS designs require a medium that can portray such detail accurately and vividly. In this case, plastic just doesn't do the job, thus resin comes in as the primary medium. To this day, the majority of FSS kits are resin of neccesity. It is simply too hard to render an accurate plastic FSS kit comparable to a resin. The standard is off the scale. Cost is high, neccesarily because of material cost, availability and demand, yes, but the detail is incomparable. 'Just my two cents...
Check out hobbyfan.com's section on Five Star Stories resin kits for an example. The clear resin armored Mighty Series are good examples of a kind of kit on a level that plastic can't touch.
Again, this isn't to diss plastic; Alot of the gundam and macross series kits that I have and play to buy are plastic, because plastic suits them fine, but all except one of my FSS kits are resin. Things are better that way.
-Z