Alot of times if not most of the time people are afraid of buying used older model speakers,either from lack of experience of buying used,lack of experience in running older/vintage speakers warrenty is a big issue with most,alot of people are also of the impression that older speakers were not properly taken care of,for these reasons people shy away from vintage.
Now my opinion is well known,im with you,i always reccomend buying a pair of 10 year old speakers that when new cost $10,000 but can be bought used for $1,500 as oposed to buying a new pair that costs $1,500 that will be worth $500 in 5 years.
Speaker tech has evolved but in most of the higher end designs from 10 to 15 years ago the cabinet design was up to todays standards,speakers do not have a lifetime,the only things that wear out on speakers are the crossovers & the surrounds,both of which can be rebuilt or redone very cheaply,in some cases tweeters that are liquid cooled can dry up & need replacing,all these are minor issues & nothing to warrant a speaker being labeled as used up.
As i said above, i allmost exclusively reccomend a used speaker in every thread but the issues of warrenty & the care the previous owner took of the speaker comes into play.