Wearable strain sensors (WSSs) have found widespread applications, where the key is to optimize their sensing and wearing performances. However, the intricate material designs for developing WSSs often rely on costly reagents and/or complex processes, which bring barriers to their large-scale production and use. Herein, a facile and affordable (material cost of < $0.002/cm2) method is presented for fabricating conductive bandage (CB)-based WSSs by electrospraying a carbon nanotube (CNT) layer on commercial self-adhesive bandages with excellent biosafety, stretchability, mechanical compliance, breathability and cost effectiveness. The wrinkled and fibrous structures of self-adhesive bandages were rationally leverage to control the geometry of CNT layer, thereby ensuring tunable mechanoelectrical sensitivities (gauge factors of 2 ~ 850) of CBs. Moreover, a strain-sensing mechanism directly mediated by the highly wrinkled microstructure is unveiled, which can work in synergy with a training-loosened-fibrous microstructure. The excellent performance of CBs for monitoring full-range strain signals in human bodies was further demonstrated. CBs would possess great potential for being developed into WSSs because of their outstanding cost-performance ratio.