I would say there is a difference between those who just happen to
have a general interest for the subject, and have, say, one instrument
"for personal use", and those who additionally(!) have professional
thus commercial interest in mechanical instruments and have a shop.

The second group, I believe, should, perhaps, feel more obliged to
contribute, than those who just have a hobby interest in mechanical
music, at least if they feel that the Digest have given them answers
to important problems in their business.

I remember no examples right now, but remember to have seen the
dividing into commercial (paid) and noncommercial (free) usage of
programs or information that are shared on the internet other places.

On the other hand, those who make this list, put time and effort down,
and should nevertheless somehow be rewarded in any case.  This would be
a calculation depending on the following questions:

1. How many will (or "have to") unsubscribe, if the Digest must be
paid for?

2. How much to charge the remaining subscribers?

3. Will the income of this be more, or less than what the income
is now?

4. If the income is higher, will it be that much higher, so the list
owners can set aside some more time to make the Digest come out more
regularly?  (I have, myself, not been annoyed about some irregularities.)

5. Will it be worth the efforts, if the income is raised with factor x,
but the number of subscribers are reduced with factor y?  (What if x is
much smaller than 2, and/or y is near or higher than 2? :-)

It already seems that the credit card solution was so expensive, that
any raise in the income caused by the convenience of paying with credit
card would overcome the costs for the list owner of having this option?
I would guess that this cost spread out onto the subscribers would be
much less than changing money or sending checks.  Perhaps the list
owners have some more comments to the economy and calculations in this?

This discussion should in any case cause us to enhance our efforts in
contributing voluntary, unless practical reasons for sending money are
difficult from a particular country.

For me, it is out of the question to send a postal money order or
cheque from Norway; the fees will be higher than the actual amount to
send.  So if I send something it will be money in a letter, but this is
no good solution for the postman, because he will be a more interesting
person to rob, if many of his letters contains money.

Thomas Henden