[Sprecker]

Just ask if s/he is for sale. If it is consider taking him home, if you can afford it that is. If he is for sale I am sure the pet store owners won't take offence to some one offering some advice like, "I would love to buy a bird like that. Too bad he seems to be neglected. Would probably be hard to care for a bird that is in that condition. Do you mind if I cut his nails so I can hold him?" Any petstore I know of knows that a held animal is a sold animal. They may let you do it. Then after you hold him tell them you are sorry but you can't afford him but would like to maybe buy a toy or 2 for him/her instead. There is no way the store owner/manager/employee will say no to a sale.
Just check in with him every once in a while and see if the owner kept the toys in the cage or tried to resell them after you left.
It tough seeing a little darling in that kind of condition. I have purchaced 3 fids because of the condition they were left in. The most recent was a moustache parrakeet that was caged with 2 cockateils after he was moved from a cage where the other birds had totally plucked his tail feathers. I was crushed when I saw the little guy. He seemed happy and was playing but I couldn't believe they left him with the other birds knowing what happened with the last cage he was in. Instant sale for me.
The other 2 I bouhgt when SuperPet was bought out by Petsamart. They took all their parrots that used to share a room with cages and play gyms, and put them in small display boxes with no contact with the other birds other than sound. I couldn't believe it. So I bought a Red belly and a Senegal. I got the senegal day one after the store changed names. The Red belly I had to save for and took almost a year to get. S/he is here now and is slowly coming around. ALl that time in the small box has made the poor guy a little clumsy and jumpy. He has a big cage and he just sits on the food dish all day. That's all he did at the store aswell.
Breaks my heart to see these things happen.