Sorry, Skye
The cup takes more work? Seems like it would be the opposite.
So long as the egg fits snugly, the side walls inside the cup can be straight with a small amount of smoothing at the bottom. Hit it with a forstner bit to get the lion's share of wood out of the way, then smooth the bottom out all cuppish like. Part the sucker off and call it done. It's not got quite the smooth look, but it'll work if it's paining you to do it.
Something you HAVE to learn if you do shows: Shortcuts will get you "off the shortlist".
At the beginning of the show, women walk by and finger LOTS of stuff. They determine which booths they want to return to (they have to tour the WHOLE show, in case someone else has the SAME product, cheaper). But, if they touch your stuff and like it, they will ask or look for your booth number (You have MADE their "short list".)
IF you display ANYTHING that is done in a mediocre manner, ANYONE who touches it will not buy ANYTHING from you. So, a quickly made "egg cup" that isn't fully sanded will put you "out of the running" for the $150 fountain pen.
If you don't have the time or the inclination to make a product to your own standards, don't make it at all. You'll gain sales.