Not that either of the below will fix the cost issue, but Schlumberger sell open hole packers, they even sell transport tube isolation valves, to allow of complete shut off of zones (not that I think you need these to just isolate a shale section). Welltec also claim to sell an open hole packer with shunt tubes through it. I am not sure what the other companies offer, but I would contact Halliburton and Weatherford too as they may have something of use for you.
If you are looking to save some money when using alternate path screens, you could run them in stands (if the rig supports this), and then gravel pack without washpipe. We have been doing this for a while and it brings ATP gravel packing down to a reasonable price (we actually do it to reduce ECD). There are obviously some sacrifices that have to be made while running in this manner and need to be considered in detail on a well by well basis. Things like fluid displacements and not being able to wash down etc. This might also cause you an issue inflating you packers unless you run the check valve type ATP screen which again might be cost prohibitive.
Finally on the note of needing to isolate the shale section, this is obviously very field specific, but my question would be do you really need to isolate the shale section? If you can keep it stable enough to get the screens in the well. Will it disaggregate to such and extend while gravel packing? If using an ATP system (or potentially extremely light weight propant) are the velocities really enough to scour the shale and contaminate the gravel pack, to an extent that will cause a significant impairment? Or is this something people have worried about historically that has come from bad practices and they put it down to shale issues?