If you can afford an XB1, you can afford a PC that can run F4. If you're on a really tight budget, get an AMD APU and get a dedicated GPU later on.
A high-end A10 will have integrated graphics capable of running F4 (although you will probably have to play in 720p on low details to get a playable framerate.)
They cost somewhere around 120 bucks where i live. Then you just need a PSU, a Case, a Mobo and some ram. You can get the whole thing for a lot less if you buy used.
If you can manage 400, you can get a faster CPU (still AMD, Intel is way better in terms of performance, but AMD is always first choice when you buy on budget) and a dedicated GPU (like an r9 270 or something similar.)