I have made these a few times and I think it's a great idea, I LOVE crisps and I regularly have a packet pf crisps almost everyday - within my syns of course. Even when making the potato crisps and synning them I'm getting double the amount of crisps that I normally would and knowing that they are not cooking in oil/deep dried it's a healthier option anyway. I think that if you enjoy them it shouldn't really matter if you have to syn them, you get much more for your syns than you would in say a normal packet of crisps that can be around 7 syns (for regular crisps) and then around 4 syns for the better varieties like velvet crunch.
I do think that if you have them WITH your dinner as say a side order I do not think they should be syned. I have made an oven bake with these using baked beans, ham and cheese and layering the crisps a bit like lasange as they are just potato it was nice and a little different.