that looks quite a bit like the impacted crop we have been dealing with. It was that low... I can send some pics. I think my wifes thread on this topic has the pics on it. I am no vet or chicken expert, but our limited experience and googling gives us a little perspective. We tried the mineral oil, and diet solutions to no avail. She was fine for quite a while but it just got bigger and bigger, until she started having trouble eating. You might get locky with oil and massage of the area, take her food away at night, etc. But if not you will need to decide
1) spend 3 to 4 hundred to have a vet clear it out
2) put the bird out of its misery
3) open the crop and clean it out
The further problem is why the crop is impacted. Sometimes its just a bit of bad luck that starts th eblockage and it gets bigger and bigger. But sometimes its a systemic problem in the bird so even if you clear it out it just comes back.