Tweeters aren't really affected by the cabinet (just the baffle) so in that case you really do get what you pay for.

With woofers the extra $$ doesn't really buy you flat response as much as it buys you low distortion, low resonance frequencies, high excursion etc... -- all things which are hard to compensate for with cabinet design.

M60ti, VP180, QS8, M2ti, EP500, PC-Plus 20-39
M5HP, M40ti, Sierra-1
LFR1100 active, ADA1500-4 and -8