LOTR had helicopter shots of the cast in full makeup and costume running or hiking along mountain ridges in inaccessible parts of New Zealand. Even crowd scenes shot for real up in the mountains (albeit less inaccessible ones in that particular case). For that you need a whole infrastructure just to support the flying, let alone the makeup artists, costume department, camera, lighting, art departments etc etc. The logistical effort is huge and New Line realized those films couldn't be done on the cheap. They spent $200M and even then that WAS, effectively, 'on the cheap' considering filming in NZ was comparatively inexpensive (and that they got three films for that price).
Not to run down the logistics of CotT and WotT, which I'm sure were not inconsiderable, but I'm sure their makers would agree they verge on being quickie, cheapie stuff by comparison.