New to D&D Beyond. I have been making several homebrew items specific to my campaigns and realized there is no area to add a cost outside of typing it in the notes. Am I missing something somewhere I feel like this is an easy fix in the coding just add a simple text box and a label, I know it has to be replicated throughout all the code where the label and textbox are called but it would be nice. Or, does nobody really care and they are just using the notes? I noticed also in the "manage inventory" section you can customize but again there is no cost area to input the data.

The magic item homebrewer is specifically for magic items. Magic items do not have specific costs, as per Rules as Written. The DMG gives a general cost range by rarity but no magic item has a specific cost. This is intentional design. The homebrewer is designed with this mind.

As a DM you would refer to the general cost guide in DMG and make a note of the price you find relevant for your NPC in your campaign, just like you would for any other magic item being sold.