As an occasional builder who used to do a lot, I've found the hasegawa and tamiya kits WELL worth the cost. The molds are generally newer, and most of the inexpensive mass market kits are originally from very old molds. That means mostly lower standards for detail, thickness, accurracy and especially fit.
There's nothing in plastic modelling like the pleasure a duffer like me gets when a kit just falls together. Less sanding, less filling, smooth lines, less tedious task work, great result. With the newer hasegawa and tamiyas, it's pretty common to have tight, almost invisible seams with sparing application of liquid solvent glue alone -- the resulting plastic gel becomes its own filler in the beautiful seams.
I found Squadron Hobby online to be a great supplier, btw.
Ah, just makes me want to open the closet and root around for that half finished D-Hog or the Hellcat i got the detail set for....
Nah, I'll just up another sortie/