I'm not sure what you mean by 'cheap' but the actual cost to buy retargeting ads is almost always significantly more expensive except for really large brands.

I'm not sure what you mean by 'cheap' but the actual cost to buy retargeting ads is almost always significantly more expensive except for really large brands. A regular sized furniture store might have 100k unique devices in their retargeting pool, but a prospecting (acqusition) audience (lets say in-market for furniture) would be 500k+ unique devices.