I just checked my royalty/download statistic at DT and while in general the trend is positive, this month is surprisingly low especially since we just had an price increase at DT. Maybe more are switching to subscription because of the price increase for pay per download but not for subscription? But maybe it is to early to tell for this month, but what is your experience?

Here are my stats:

It looks like you have had a better $/download average than me in the past, but i haven't noticed any downward trend recently.  Perhaps the contrary. 
Dreamstime has done a good job of raising comissions!