I assume it's a bit chicken and egg - marginal costs of new customers/extra searches is relatively low, it's the crawling & development/SRE that's expensive - so should (or at least could) come down as more people adopt it, driving further adoption from relative cheapskates like me?
It seems great, but I use DDG 'bangs' (which are also a Kagi feature) loads of times a day, rather than going directly to websites - especially !w & !wikt, !arch & !aur & !archpackages only slightly less - I'd blow through the monthly limit in no time on that alone. (Which also seems a bit unfair, they're just redirects, not using index, there's an argument they shouldn't be included? I suppose if you're so motivated you can work around by using Firefox's feature for it instead of search engine anyway.)
Edit: oh wait, I just found in the FAQ that 'bangs' actually aren't counted as searches. I may have to trial it, see how many searches I actually use how quickly. (And how reasonable the 1.5ç overage seems in my usage.)