How to show single item price, but only allow order if

Have you thought about just writing the price for a single toothpick in the description of the product? Then, the “unit” of toothpicks is a multiple of 30.

Yup, but would be neat if price would be in next to product.
It looks cheap for the customers eye ??

I tried some variables and attributes, but didn’t get it yet

I wonder if you are still working on this. In any case, this might be helpful to other people who have to figure it out.

WooCommerce has a few extremely helpful filters that you can use on quantity boxes. I’m still working my way around these, but you should investigate the following filters:

woocommerce_quantity_input_min
woocommerce_quantity_input_max
woocommerce_quantity_input_step

These filters are used whenever a quantity box is displayed, and will force the minimum number, maximum number, and the steps in between.

You could set them on the single-product.php page template, and you’ll also need to set them (or use them) on your “cart” page, in the template that you can overwrite.

You can also over-write the quantity box (using the template woocommerce/global/quantity-input.php).