of course with 43K domains you could run your own Registrar and you won't be the smallest.
Note however that managing a Registrar business is not just a matter of finances, you also need to comply with an increasingly amount of technical, legal and administrative constraints imposed by each Registry and by ICANN.
Now about money, even if you are your own Registrar you are going to pay the annual registration fee or renewal feel like whichever else Registrar, actually the Registration fee for .com and .net in particular are fixed and regulated by ICANN (in accordance with the Registry), in other words Verisign (the .com/.net Registry) cannot increase (or decrease) prices without prior ICANN approval and all Registrars regardless of their size and volume are paying exactly the same fee for Registration to the Registry and to ICANN. The current price paid by ALL registrars for a .com domain is $6.86 plus $.20 to ICANN, in other words whomever is offering the Registration or Transfer for below $7.06 is selling below cost and be assured you are going to find Registrars selling below cost but in general it is for a limited time or for a particular promotion but for none of us the real cost will be below $7.06 and I am not including handling fees or credit card processing fees.
Once again even if you are approved by ICANN, and it can take a while and you create all the technical, legal and administrative infrastructure to handle your names, it won't cost you less than $7.06 per domain, without including server fees, credit card processing fees, annual ICANN membership and so on.
Another approach to reduce your initial migration fees, would be to migrate progressively your domains while they are expiring, this way you can in average divide by 12 the initial amount needed and anyway you would have paid the same amount or a greater one to your current Registrar for renewals. We are currently offering .com transfers below cost at $6.90 and .net at $4.99, meaning at our current transfer price it would be cheaper for you compared to running your own Registrar.
I hope you will have a look to our offer and taking in account the relatively high amount of domains you represent I will be pleased to be your direct contact in case you decide to work with us, either now or in the future, there is no rush.
Regards,
Marco Rinaudo - CEO
Internet.bs Corp.
http://www.internet.bs