I will offer a maximum of 40% for wholesale work, as that is the way my pricing structure works. It will depend with a few pieces, as making a batch of items may take less time than making them individually, but if it doesn't, I can't offer discounts on my labour costs.
Perhaps let them know what you would rather your terms would be. Have a good think, and add some policies into your shop about how you might take wholesale sales. Perhaps you would only offer 50% if they purchase 100 units, but from your pricing structure, it sounds like that would be a kick in your profits. Work out a pricing structure specifically for making items in bulk
Is there any way you can create them faster or streamline your process?
Something along the lines of this might help:
"Dear --
Thank you for your interest in my ----. Due to these articles being handmade, I would be happy to to offer a --% discount for wholesale lots. I already try to price these items as fairly as possible, being fair to myself whilst also being fair to my customers, so as a result, my pricing structure would not allow me to offer a discount of 50%.
Should the --% discount be agreeable, please do let us know so that we may get started on your order for an estimated dispatch date of --.
Kind regards,
Cassi Jo and Casey Perez
BohemianHabits"
I might also suggest putting your prices up slightly, which would allow you yo make a decent profit, and not take such a massive hit with a wholesale order. With a wholesale order, you should still be making back your materials, expenses and labour costs- as well as profit. You shouldn't be breaking even. Ever!
Good luck :)