Markup / margins vary by niche, by location, by type of retailer ...
2x isn't at all unusual for specialist stuff, just as at the other extreme discount food supermarkets in Europe used to be about 3% and they were jealous of the 5%+ being made by the UK supermarkets. One is very small volume, one has huge turnover.
You just learned a valuable lesson about the importance of understanding cost structures.
I once looked into selling a food product through various routes. Supermarkets are hell to deal with. Specialist grocer / delicatessen types have slow sales, need big markups (albeit nowhere near 2x), and need a catalogue full of lines to choose from. When you only sell a few per week and sell-by-dates means you don't want to hold more than 6 weeks stock, you need to buy a mixed basket of stuff just to amortise the cost of shipping. That venture didn't make it past the market research even though the product was great.
It's all about power and who controls access to the customer. Unless you sell a "must have" product, the retailers don't need you, there's always someone else.
The next scenario you'll encounter is galleries or whatever wanting your goods on consignment. You take all the risk, put your product in their store at your own cost and they only pay you if and when they sell it :-(
Online selling has opened up an opportunity for a lot of people to sell a lot of stuff straight to the consumer. That includes etsy. Before online shopping and the explosion of delivery services these businesses wouldn't have existed because the economics don't work. Mail order would have been reliant on small printed ads in lifestyle magazines and newspapers for a single item or limited range of recognisable products..