I don't think so. Consider this; hypothetically, let's say comedy comics have more subscribers than horror comics, would is make sense to lower the threshold for horror then? I'd say no.
I'm not 100% sure why there is a threshold, if I were to guess it'd be to make it easier for tapastic to manage. If you have less than 250 subs, then realistically you aren't going to be generating anything more than a few dollars every now and then, and there are going to be some costs involved in managing any kind of financial relationship. If tapastic cuts out everything with less than 250 subs then a significant amount of those management costs can be avoided without losing much revenue at all.
So from their perspective, it doesn't matter what content you make, all they need to think about is how much money you could potentially make.
Any argument that different types of content deserve different thresholds is about fairness, which doesn't really matter from a business perspective.
The only reason in my opinion to lower the threshold would be if novels tended to generate more per subscriber.
