The answer to your first question is no, you have no idea what the seedling will look like. It could be amazing or it could make dog poo look elegant. I have no idea what the odds are for or against getting a nice plant from a handful of seeds. It would depend on the parents for sure but yes even expensive seeds can yield plain daylilies.
Buying seeds can be a way to get genetics that you otherwise wouldn't be able to or it can just be a fun hobby.
As far as expectations, I would expect at least some germination (though there are likely crosses that do not result in viable seed) and I would expect that the seeds I am buying are from an honestly and correctly labeled cross.
