Well the absorbtion is great for removing flutter echo and highly prominant room modes you will actually need some diffusers at some point to reintroduce activity into a room, or posssibly some reflectors if you find certain frequency bands are noticably missing.
i've been in studios where the treatment has been purely absorbative and the result is not a pleasant enviroment, if the sound is too dead it will actually make working fatiguing.
The good news is that with most absorbtion that high frequencies tend to get dealt the biggest blow and that windows actually reflect high frequencies and act as bass traps, so their impact on a room is not always as negative as people make it out.
Are you going to be attempting sound proofing within this same budget? Please say no.