Litsea Cubeba (aka May Chang) is also another option for a bright, lemony scent, and it sticks fairly well.
I personally think that Litsea smells a lot more "generic citrus" than lemongrass, and it's just as cheap. Lemongrass smells like... lemongrass, like herb and citrus together. Litsea sticks quite well, too.
That's interesting, I did not realize. Is the reason because to get a good scent you need too much of the EO and that makes it expensive, or you need too much that it ruins the recipe somehow?
...
As you've seen (from posts after I quoted this one) the scent can easily equal the cost of everything else in a recipe, but IMO that scent is what makes handmade soap so interesting. Colors and pretty swirls are fun and challenging, but when you stagger into the shower on a Monday morning you won't notice them. But that scent will penetrate that foggy mind and help start your day off right.
Economy of scale makes a BIG difference when buying scents, too. Buying a single ounce of NOW brand at a brick-and-mortar store is
very expensive, but 2 oz from some place like Brambleberry is often actually cheaper (before shipping). By the 7-8 oz bottles, you might be paying a quarter as much per ounce.
One last thing about "unscented soap." If you don't use an EO or an FO, the subtle scents of things like cocoa butter and coconut milk
do come through slightly in finished soap, IME. They are quite subtle and may not survive a very long cure, but they're detectable (to me) for several months, and if you're only making four bars at a time.