There's no mention that it's just ~10 words you are getting from signing up, once you are done with that you are prompted to upgrade ($18 for the next 370 sounds). Apart from that there were also a bunch of duplicates in the free ~10 words you see after signing up. ("kalte" was probably asked 4 times)
I don't know if it's OP's site but I'd include a demo that is actually usable without signing up and make it obvious that it's not "free".