I own a resale & consignment store. It sounds like these new biz owners are unfamiliar with how consignment should work for what we call an "Artist Consignor." Regular consignment rates are usually in the range of 40/60 to 50/50 for gently used items. But for someone who is producing/crafting/constructing pieces themselves the rates need to be different. I did a LOT of research before I picked up any Artist Consignors. I found the range of normal rates to be 25-45% for the store to keep. We set our rate at 30%. Obviously, the Artist needs to be able to recoup their investment and make a bit as well.
Keep in mind what the store is providing to you. It is larger than just the sale of pieces. Yes, you could probably make more per piece selling on your own at craft shows or through word of mouth. However you will also benefit from the exposure. When the store pays for their advertising, whether they specifically mention your pieces or not, you will benefit from that at no additional expense to you; it draws people into the store which means more eyeballs seeing YOUR product.
There is the matter of sales space, as well. I know exactly how much money each square foot of selling space makes for my store each month and every inch is precious. Space is always a challenge and I will not waste it on unproductive or unprofitable product. If I cannot make enough on something to justify taking up space the product is discontinued in short order.
In addition, you have a skilled sales force working for YOU on commission…if you don't make money, they don't make money. I'm a good salesperson (it's what I love) and I train my people well. While my Artists are busy with their families or making other pieces we are busy selling their pieces! They get to focus on what they do well and we focus on what we do well, and that benefits both parties.
I've worked hard for the past five years to establish a stable, large clientele that have come to know my store as a unique place carrying local product at reasonable prices. If your product is added to my store's product mix you are guaranteed exposure to clientele you probably would not have access to otherwise…that's thousands of "hits" per month, to put it in eBay store terms. You benefit from my advertising (radio, print, tv, email), expertise (display, salesmanship), location & clientele (no overhead for you, established client base), and equipment (signage, displaying fixtures, credit card machine/Telecheck, invoicing, collection of funds at no charge to you), all for that 30% fee.
All that to say, maybe do some research on your own and print some sample Artist Agreements out to show to this consignment store. Or maybe this particular consignment store is not the right fit for your product and you need to shop around.
Best of luck in whatever you decide!