Most people will say 3 to 4 times the cost but there's alot that goes into determining price.
So things to consider...
1. You seem to already know the average cost for a bar of soap in your area and this is important. Your market will only bare so much price. I upped the price of mine last year to $9 and sold maybe half of what I did the year before. Then in January, I lowered it to $8 and sales skyrocketed. So know your market. Know what others are selling. Know what is wanted (talk to potential customers and listen to what they want). Know what you have to offer. You don't want to sell yourself short, it's true, but if you are priced too high to buy them, then people won't buy. Contrary to what some people think, the public is not rich and right now many are struggling. Our soap is a luxury when they can pay 1/3rd of the price at the grocery store for cheaper stuff. Some will tell you that people are willing to spend money on things they consider worth it and that's true. But when they are struggling to put food on the table and gas in the car, which will come first? Luxury items or food?
2. The cogs matters. Cost of Goods Sold. So how much does it actually cost you? Materials, supplies, packaging, shipping, website, fees, taxes etc. The cost for your own take home is not something I'd include in this.
3. Your wage. Personally, I don't account for my own time to make it, I'll be using that time on something regardless even if it's playing video games. And I find making stuff to be fun so it isn't really work for me. If you're just starting or not making a true profit yet (it takes up to five years for a business to make a true profit), it's probably not worth building a wage into the business yet. For me, I did meh my first year but wasn't in business long and people didn't know me. My second year I did great. My third year was a struggle (that's last year). This year so far started in January and ended March 14 when I broke my ankle and everything ground to a halt with sales dropping to zero even online. I'll be going back on September 1.
4. So keep that in mind. You will have good years, and you will have bad years. And while there are people who utterly refuse to go with the ebs and flows of business, if it's a choice between lowering your prices or going out of business, you need to consider which one is more important. I chose to lower my prices and it worked.
5. Also, as people get to know you, your customer list will grow. You can raise your prices then as your product becomes in demand.
Just some things to think about.