Artist are a strange bunch. No other professionals in their line of work would deny pay for their services. Dentists and Doctors surely would never see a patient without some sort of pay (at least not in America). Yet artists will willingly for go pay to express their art.
My hopes one day is to earn a living from comics, granted I don't expect a career of posting comics on Tapastics to be the answer to that dream. However, I won't turn away someone that's willing to invest in comics, like what Tapastic is offering through something like a subscription service, so I can start earning back on the work I put in. Also, I agree that there should remain like a sampling of comics available for free (maybe the first couple of issues?) and then readers can choose to pay subscribe to see more? And definitely, pages that are already posted for free should remain free.
Perhaps something like Youtube's model of paying content makers would be a better model to try and emulate for comics? Somehow they're able to pay Youtubers a good amount with most of their videos still available for free viewing. These are my thoughts on the matter at least.