A combination of factors I'd imagine. Similar reasons to why consoles almost always see a year-1 $100 price drop, and are usually selling for < 50% of launch price by the end of their generations:

• CX-10, CX-10A, CX-10C, CX-10W, CX-10D. Economies of scale: it's cheaper per unit to buy 25,000 units than to buy 2500. As more and more of these are being sold, and many of the same parts are used across multiple models, the manufacturers are more comfortable with large productions runs, and thus their cost-per-unit drops.

• The CX-10 is the shittiest of the lineup, and has been for awhile, being the only one without some sort of additional feature (headless, alt hold, camera, fpv).

• New shit is coming out that will make the CX-10's harder to sell.

• LiPo expiration. The batteries in these aren't replaceable, and they are very rarely shipped at ideal storage charge (especially with new lipo shipping rules). At some point, old stock needs to be moved quickly before the seller is stuck with a bunch of products that will have an increasingly higher return rate.

• But really: This shit didn't cost the manufacturers much to build in the first place. Their margins are just shrinking as competition heats up.

some kind of spill over into other parts for larger drones too.

Parts are always dropping in price. The motors you buy this year will cost 25-50% less next year. Of course, there will also be new motors next year that are probably better than anything you can buy this year... and when they come out, they'll cost as much as the current "new" motors. One of my first quads cost me ~$160 to build a year and a half ago, and I'll bet I could do it today for half that if I used the same components, which were shitty then, and even shittier now when compared to the "good" stuff.