This is a perpetual question,
Your obviously half way there, if you know what your costs are... Kit, blank, presentation(box/sleeve) TIME, CONSUMABLES( glue, sandpaper, drill bits, ELECTRICITY)any selling costs (shop fees or stall fees) then you add your bit for profit..
DON'T undersell both yourself and other craftspeople by 'I'll just cover my costs' some people do this as a hobby, some as a business.... Quality WILL sell at the right price...
I hope this helps