I haven't found any teaser pricing and I'm almost an S.M.E. regarding Bookbub. The BB Featured Deals was $613 for broad US and international exposure. Rather worth it, though, since in only 3 hours I've made 315 sales... about 6 times the amount of sales I made in two-and-a-half months.
Did you pay for cover art? There is talk of free AI cover art either now or soon.