Walmart offers the Stalwart 60-Piece 3.6-volt Cordless Rotary Tool Set, model no. 75-36035, for $8.52. Choose in-store pickup to avoid the $4.97 shipping fee. That's tied with our mention last week and still the lowest price we've seen. (It's a current low by $14.) It runs at up to 10,000rpm and comes with bits for sanding, polishing, engraving, and drilling.