Bob,
Within that budget, you should have no issue getting something that can make the 4 mile hop, and possibly the 10 mile hop. With line of sight, 10-15 miles is easily doable with some slight directionality. Early on, KC5DFC connected in from Rockwall using an NanoStation M2 on his fence at home and was able to establish at 15mbps link to K5UTD. I personally watched video from a webcam he setup as well.
The NanoStation M2 is the most popular choice for client radios. The airGrids are nice too. If you're wanting to spend a few more bucks, a Rocket M2 with some form of dish is also a good choice. The reality is there are plenty of radios to work from, and I always work backwards from the Downloads page on the AREDN site to verify the current offerings are compatible.
73 de KE5GDB