When I first started selling online I was quite naive. I didn't really think it through, but imagined that if I priced something at £10, and the listing fee was 20p, then I'd made £9.80.

Not so.
On
Zibbet, premium sellers pay a monthly fee, basic sellers have free accounts. Even that isn't *really* free though, as of course Paypal take a cut, and there are supplies to buy (including packaging, business cards) and my time to consider.
On
Etsy and
Folksy there is an initial listing fee and a percentage commission when something sells - and of course the inevitable paypal fees. For a UK seller, there is also the currency exchange rate to keep in mind...but let's not go there today other than for me to say I use
Dollars2Pounds.
I asked Mr Nifty to set up an Excel spreadsheet for me, which I'm now offering to you as a download. It's set up for me, of course, as a seller in the UK. If you are NOT in the UK, your paypal fees may vary depending on currency.

Enter your selling price and shipping charge in £. find the current exchage rate by clicking on the link and enter it. The calculator will then enter your $ price (rounded to the nearest $) and subtract the Etsy/Folksy/Paypal fees. You can then enter your costs - for me that is yarn, beads, wire, packaging, business cards - anything that I have to buy in order to maintain my business. You might also need to include costs for your blog or website. The final figure is then your profit, your "wage". I charge for my time and expertise - it's entirely up to you, the maker, whether you do this.
If you end up with too low a final figure, then you need to reconsider your pricing, maybe even reconsider what you're making! Good luck!
Go to my
website to find the calculator and click on the link to automatically download a zipped excel spreadsheet. Any problems - please get in touch so we can fix it.