Hey if its working for you then for sure keep doing it!
Most of the time the crafters I meet say "oh my gosh I am only making 2.00 per hour!" Or like you they say they make 15.00 per hour but cant sell anything. So I say kudos to you if you can make 15.00 an hour and still sell things.
I still think though it would be impossible to really know. Especially if you are at craft shows. Because is your hourly rate including that? Or just the time to make the item? See what I am trying to say? Our last show was 3 days from 8 am to 10 pm. Long long days. I could try to figure an hourly rate which would be a nightmare. Or I could just take what the show cost me, the cost of making the jam sold and subtract sales and then I know what I made.
When it comes to tax time most of us will use this method. Once you do your taxes you will see what you really made or did not make.
For me I am always making several batches of jam at the same time. So I might make 4 batches and then hop on Facebook

for 30 mins. But thats the beauty of working from home.
Imagine being a retail store owner and trying to figure out your hourly wage. Its much the same concept in crafts because we all do have a retail store especially if you sell online.
I have never lost money on a craft show but see a lot that do. I hate it for them. Especially in this economy when people are trying so hard to make extra money.
It always shocks me when someone asks me to help them price something and they have no idea of what it cost them in materials to make the item.
Anyway this is not meant at all personally. I just love talking about pricing and the business end of crafting.