You can buy the Apple-branded stuff. Or you can buy a KVM switch, a SSD, and two sticks of RAM off Newegg yourself. Monoprice has HDMI to DVI converters for less than $3. Upgrading the internals is about as challenging as upgrading the internals of a non-Apple laptop. It's honestly not that hard.
On the off chance you don't have a mouse, a keyboard, or a display, you can get a decent mouse for around $5, a decent non-mechanical keyboard for $30, and a high-quality display for $150. All three of these will improve your productivity on your laptop if you're not traveling. If you don't have a laptop or a desktop...how are you developing for Android to begin with?
Well, this requirement wasn't in the original brief. And in any case, you're trading your own labour and domain knowledge to shave a few dollars off. The scrounging you've mentioned is only a little cheaper than what I've mentioned - my point is that it costs more to set up a mac mini for a developer (rather than a headless server) than the throwaway line presented. Even with your cheaper, more-effort-given-to-scrounging pricing, the monitor + HIDs alone add 1/3 to 1/4 the price, never mind the ram or ssd.
On the off chance you don't have a mouse, a keyboard, or a display, you can get a decent mouse for around $5, a decent non-mechanical keyboard for $30, and a high-quality display for $150. All three of these will improve your productivity on your laptop if you're not traveling. If you don't have a laptop or a desktop...how are you developing for Android to begin with?