Good idea!!!!!

No I do not think it is too much if it is a good pattern. If you really like it just think one spool of aurfil or 2 yards of on sale quilt fabric are almost the same price but the pattern is non consumable and reusable and resellable.

I am just wondering if you could make a couple to sell and then you would not feel bad buying the pattern. I watch that QVC sometimes when they are selling fabric bags. They sell for lots of money, much more than what it would cost to make one. And, most importantly, it would be a custom colored one you made.
I personally love to make bags and wallets. They are so fun and very practical. I made all of my sister in laws a bag for christmas last december, and they were a Big hit.

You could always sell the used pattern when you're finished to help recover some of the cost. I don't think $13 is a bad price especially if the instructions are detailed, but that's up to you. As others have said, the other option is to make and sell a couple bags to cover the cost. Unlike quilts, bags typically are considered utilitarian and cannot be copyrighted so you could sell as many bags as you're willing to make.

there are so many free or inexpensive patterns available. I have found many patterns at Craftsy and epatterns. Also, allpeople quilt.com and allfreesewing.com. Once you get the basic idea for a purse, tote bag or messenger bag, you can play around and alter it to do all sorts of neat changes.

It's more than I would want to pay, but then, I don't know what it is. I'm only an intermediate sewer so something very complicated would leave me frustrated.....

personally, I'd never spend $13 on a pattern I'd find something similar at the dollar sales at JA's, and make it similar to it.

I purchase bag patterns from byannie.com for about $10, so it is a few dollars more than what I would expect.

I look at quilting and bag making as a hobby. I could buy a quilt at the big box store for far less than what it costs me to make - but that's no fun. When I start on a project I don't try to cost justify it or make money on it (I have a job for that). I spend what I can afford and enjoy the process.

Sometimes you just gotta go for it if you really love something.