I have a product called Attic Manager (guacosoft.com/attic) which is a home inventory software with unique feature on the market - it is able to import database from all versions Quicken Home Inventory programs. Currently, it is only product on the market that does that (probably because it is not so easy to do, I spent months reverse engineering their custom file format).
I used to sell it for $19.99 and got about 30 orders per month consistently in the past 3 years. That's around $600 per month gross (my actuall earnings are lower, because of payment gateway cut, but that is irrelevant here because it's fixed percentage of gross price anyway).
After reading that "you should charge more", I upped the price to $29.99, a 50% increase. The experiment is still going on, but in the past 3 months I got only 42 orders. That's 14/month. 14*$30 is $420 per month, or 43% less than before.
So, all the "you should raise you prices" is just an idea to consider and maybe test, but I wouldn't trust it blindly.