We use the highest quality shirts and deliver them with the most affordable pricing.
Does this imply that the $25 price is the lowest possible point at which the OP can attain reasonable margins? If so, they really need to reevaluate their infrastructure, as $25 for a text-only tee shirt is very, very high, and the OP is likely being ripped off by their suppliers.
Given the price, I have doubts about the willingness of potential customers to purchase shirts of this sort. The precedent for comparable services like Teespring and even for individual shirt vendors seems to be $10 to $20, substantially lower than what the OP is charging.
Other than the pricing, I'm not entirely sure whether hashtags would make suitable shirts. Hashtags tend to be highly ephemeral, and most cease to be relevant within a few days. Most people keep shirts for years, and thus would be likely be wearing these shirts for a period far longer than the life of the hashtag. It's a novel idea, but at the end of the day it's trying to turn what are highly transient cultural artifacts into something permanent.