I don't know anyone dumb enough to pay $30 for someone to mail their friend a meme, it's just a wildly dumb service that isn't going to profit you in the least. I guess you didn't notice that people use phones, emails, social media, and so on. So you won't be getting any larger orders as the service is dumb and I would just avoid it entierly.
You might be kind of hard pressed to find a market for people willing to give you Bitcoin just to send memes to someone, but I guess it is possible to make money off of it.
The biggest thing I see here is that you're charging $30 for a postcard. Charge something like $5 or $10 with mail included and you might have some people interested in it.
While it's always better to make more money when possible, $30 for a postcard (resulting in $28 of profit) is going to be next to impossible to justify.
Going to second this, drop the price down and maybe do something original with how you present and you MAY (low chance) make some money off of it.