I'm not sure do candles are used somewhere else than just in the glyph magic. If yes please correct me.
My proposal is make candles twice same worth. Now they are worth 4 silvers each. I propose make them worth 8 silvers.
Because producing them gives almost no profit and also using them in the rituals takes some time. Consumption 100 can take a few hours.
They're used for lanterns and other sources of light (as opposed to oil lamps or torches). They make a decent amount of coin, I feel. An hour or two at the task generates several gold coin, and if you can sell to other PCs you can always charge extra.