Thanks for taking time and the detailed reply.
While I still disagree with some of your points, I understand that you must setup a business model according to your own business goals.
Still, I'd argue that your model is not logical, even from a business point of view. If you allow me, I want to suggest a different model with a different set of restrictions that may just solve both of our concerns. So, here goes nothing:
Don't put any restrictions whatsoever on the number of results per search.
Instead, put restrictions on search volume, i.e. the number of allowed searches per month. Higher accounts will have higher number of searches per month.
Then, if an account reaches the monthly allowance of search volume, the users should be able to buy extra search volumes with additional one time payment. This can be much costlier than monthly payments, just to attract regular users towards higher capped monthly subscriptions. However, these credits should not expire until used and non-monthly subscribers should be able to buy these one time credits as well.
There are many SAAS & Web Apps out there that use very similar model successfully. Putting restrictions on number of searches doesn't make any sense whatsoever. It needlessly reduces the quality of your App. If any competitor comes with the model I've suggested, I guarantee you, you'll lose business to them, while they'll still be more profitable compared to your model.
Besides, people with higher number of domains will definitely need higher number of monthly searches. But for a single search, nobody likes less number of results even after paying.
For example, say I pay you $10 next month, but I only needed to use your service for one particular search topic in the entire month, with say only 20 total searches. Why would I give you $10 if I only get 25 results and then have to do all the gymnastics with filtering to make it 100 results?
If I get 100 results with gymnastics anyway, why not give it to me at once and then put restrictions on how many searches I can perform!
Obviously someone with thousands of domains will need more number of searches than me. But no one is satisfied with less number of results.
Think about it. Who knows, perhaps you'll be able to come up with a far better pricing model with these suggestions. If not, then I wish you well, but I'll make my peace without your service.
All the best wishes
Fayaz.