I don't buy into $4,000 being the same price they were back then, if they were $666 in 1975, then we have to look at other items as well. In 1975, we bought a brand new Ford F100 truck, for $2,600, in today's money, that's about $12,100 or so, try and find a new truck for anywhere close to that now. If we're going to believe one of those inflation calculators for one item, then it needs to hold true for all items.
One could argue that a lot more goes into a modern truck or set of speakers, or anything built today then in 1975 but the same would hold true if you looked at items made 40 years prior to 1975.
What we have to look at is the buying public and how much spending cash they have today vs. 1975 or any year prior. In 1975, we bought that truck cash, along with a new car that year. The likely hood of buying a new F150 for cash these days is slim. If it were say $12,100, then maybe, but the last time I priced a new F150 here it was well over $30,000 with a base price of $28K.
So either inflation is far greater than the 3.73% that those calculators figure on, or manufacturers are just price gouging these days.
I've been a long time fan of JBL, but the likely hood of me ever spending $4K on a set of small speakers is nil. For a set of Ti250's or similar, maybe, but again, there's plenty of vintage originals to be had.
Besides, when was the last time a reproduction model turned out to be as good as the original?