This might be related to the bing API. I'm pretty sure Bing hiked their API access prices, effective may 1st 2023. Custom search is way more expensive than regular search too.
But I'd think duckduckgo wouldn't really be affected by public pricing, and that they have some sort of huge discounts and contracts that would protect them against this. If they pay anything that is, since I thought ddg generated revenue from using bing. Though Ecosia seems to have the same issue so who knows.
https://www.computerworld.com/article/3688574/microsoft-more...
Source on the price increases, seems like the API is now 3x to 10x more expensive (I used the MS docs directly but the article shows the previous rates too).