A minimum of 700mA on USB is absolutely what a Raspberry PI takes and is listed as such on their website. Their site also says that each of their USBs port can

A minimum of 700mA on USB is absolutely what a Raspberry PI takes and is listed as such on their website. Their site also says that each of their USBs port can handle only 100mA, and little more. [1] "Generally speaking the model B raspberry PI was designed only for <100mA USB devices! That is because the PI's PSU was chosen with a power budget of 700mA in mind of which 200mA were assigned to the two USB ports, so the raspberry PI's (poly)fuses were designed only for <100mA devices, and typical 140mA polyfuses will have as much as 0.6 volt across them when drawing currents near the 100mA limit. As a consequence the USB ports are only directly suitable for "single current unit" USB devices which according to USB specifications are designed to work with just 4.4 Volt. Not only do non single current unit devices draw more current, (causing greater Voltage drops, and greater stress on the fuses) they also might require 4.75 Volt to work. Therefore any non single current unit devices will only work when powered from a powered hub." Plugging in devices that take 150mA or more almost always cause problems. Sure these things aren't within the USB spec, but neither is my 2A iPad 3. As for $25 vs. $35, oops. I pre-ordered months ago and had forgotten what I'd paid. [1]:http://elinux.org/RPi_VerifiedPeripherals http://elinux.org/RPi_VerifiedPeripherals