Greedy Subscribers vs Impressive Earnings - What Shall I Do?

Ok, a lot of the people here have been building lists for a lot longer then
me so I thought I'd run this by you and see if I can get some solid
advice.

I have been building my expired domain subscriber list for almost a year
now by putting together lists of 100+ expired domains 3 or 4 times a
week for my subscribers. I would then post about it the next day on
my blog to entice new subscribers, and so it went round and round.

Over the period of almost a year I have built a substantial list and have
had some solid revenue ( nothing too impressive ) via affiliate sales of
said expired domains - I linked each domain to Moniker/Godaddy and
some willing subscribers bought through my affiliate links.

Ok, recently I came upon an idea to provide a premium list service
in addition to the free expired domain lists that I had provided to
that point. This is important: I did not break any promises I made
to people that subscribed to my lists. I still provide lists of
100+ expired domains 3 to 4 times a week free of charge.

On Sunday last week, I started to provide an additional list
of 500 expired domains and called it the premium expired domain
list. For a fee of $5 subscribers can download the list to
get a better shot at some good domain names.

Firstly, let me underline this: Financially, this was a brilliant idea,
since Sunday last week I have made $970 and counting in revenue
from the premium lists alone. Most people are extremely happy
with my service and have sent me emails thanking me for finally
letting them get some quality names before the lurkers get their
hands on them. (Lurkers on the free lists sometimes grab all the
good domain names before anyone else can get a shot at them).

The thing you have to understand is that my lists are top of
the line stuff, it takes me 4 to 5 hours to put together a list
of 500 expired domains.

Ok, now my concerns. A couple of people wrote in saying they
are not happy with paying $5 for a list of 500 expired domains
as they feel they shouldn't have to pay for something unseen!
They would prefer to pay on a domain by domain basis (
which is physically impossible ). Also, some people have complained
that the fact that I now provide the premium lists has somehow
devalued my free lists ( I do not differentiate between the
free 100 domain list and the premium 500 list... the only
difference is the quantity ).

I have indicated all this to my list but I am slightly concerned about
the long term effects of this strategy but I have to be honest:
the returns have been excellent since I launched the new
feature and frankly my current thoughts are "to hell with
the complainers, if they can't appreciate my hard work, I don't
want them on the list". I pride myself in my work and I don't
intend on scamming anyone, but if they can't see the value
of my services, perhaps they shouldn't be on the list in
the first place.

I'd appreciate any thoughts on the matter.

Thanks,

John