(I am however interested to se if anyone can provide any scientific evidence as to the real benefits of free-range/organic foods)
I don’t think the answer lies in qualitative data. There are 2 points.
1. Either you care about animal welfare or you don’t
2. Either you can tell the difference between a cheap tomato/chicken/whatever and a quality tomato/chicken/whatever or you can’t
If you answer positively to either of the above then likely, if you can afford it you will pay more for the quality product.
I would add that organic != quality and vice versa. I’ve had plenty of high quality veg/meat which is not certified organic.
But without knowing provenance, organic is at least a guarantee of a certain standard of welfare.