years ago and long before I became a professional comic creator and
self-publisher I did sample inks for DC for an editor that was
interested in my work. I did them for free and I did not have a
problem with it.
Overall I enjoyed the experience. To me it was like auditioning for a
part in a play or movie. I did not expect to be paid unless I got the
part. The editor (I forget his name) was very nice, complemented my
work and promised to keep me on file. Even though I didn't get the job
at the time, just by him telling me that my work was very good was
I found out later that he left comics altogether and I then turned my
focus to creating and publishing my own ideas.
I think that "getting paid" for a sample depends on your proven or
unproven marketability in any industry. When you are an A-lister in
any industry you get offers that you don't have to audition for but if
you are new or unproven, doing auditions or samples may be your chance
to raise your value.
Just my thoughts on the matter.