There you have information about the reseller price which might help you select a cheap registrant
OpenSRS is a reseller of Tucows if i am not wrong.
$10.00 is the cheapest you can buy a domainname from Tucows
Not exactly. Actually, OpenSRS is Tucows; it's the name of their wholesale domain name registration service/platform. They also operate Domain Direct for retail sales. Other companies selling Tucows domains are resellers, or "Registration Service Providers."
Tucows does have volume pricing discounts, though they don't publicize it much or display information on pricing or the volume that would be necessary -- but there presumably are RSPs paying less than $10 to Tucows.
check this out too DMOZ Top Listeds Domains [whois-source.com]
other intense domain analysis [registrarstats.com...] and [dailychanges.com...]
you specifically asked for opensrs, but just so you know, ANY top level enom reseller can sign up you as a reseller for free (if they are so motivated) and you can buy domains with all the enom features for $8.95 (the other option is to drop $5000 on enom to get the $6.95 pricing) So far I have been very happy with that one-at-a-time situation from enom because you get all the other $5000 reseller features. Can't lose.