Wouldn't an app be easier/cheaper to provide that just sits in the corner of your normal computer screen and displays the price? That way you wouldn't need to

Wouldn't an app be easier/cheaper to provide that just sits in the corner of your normal computer screen and displays the price? That way you wouldn't need to duplicate all the hardware and software that a separate complete standalone machine would require. If you start looking at costs for a home-grown separate machine, you'd probably find that a mass-produced computer (maybe one of those el-cheapo laptops) would be more suitable and end up cheaper.