Where I live (France), an average single tank wing costs at least 300 euros, which is as much, or more, than a decent, simple, jacket-style BCD. Wings for twinsets are more expensive. And you have to add the price of the backplate, harness, cam-bands, weight pockets ...
Not sure where you are getting those prices from. BP&W tend to be about equal price with mid-high range jacket BCDs. That would be a complete set-up, based on BP, wing, hog harness, cam bands and STA.
And if I want no average wing, but one of the best wings available from the US (no dealer here), I have to pay its price in $, then its delivery, then custom fees.
Sacre Bleu!
You really order from the USA??! I don't know about France, but there are
plenty of distributers in the EU. Certainly a great selection in the UK. Much cheaper shipping, no customs...and many online stores will take payment in Euros.
Each of my single-tank wings costed me more than 500$. At this price, I can start a collection of simple jacket-style BCDs, which turn out to be the best of this kind of BCDs in my opinion.
Explain why you think that?
You say that "You can easily change components in your BP/W" ... well, easily maybe, but certainly not for free.
No, not for free..... but for a whole lot cheaper than a new BCD would cost.
BP - Never needs replacing, not ever.
Wing - Typical 3-5000 dive life expectancy. Cost to replace $350.
Harness - Typical 1000 dive life expectancy. Cost to replace $15
Cam Band/s - Typical 2000 dive life expectancy. Cost to replace $40
Now... consider the jacket BCD. One tear. One snapped buckle. One frayed strap.....and you're scheduling a trip back to your dive shop, credit card in hand.
Jacket BCD - Typical 800 dive life expectancy. Cost to replace $250-$500
Your poodle-jacketed friends may well be smarter than what you seem to think.
That's what they tell themselves.....
..............ignorance is bliss.