Plumbing Leak in Duplex

[Art Maydan]

My duplex has water leaking through the downstairs bathroom ceiling (link). Upstairs, the toilet is directly above this. I had a contractor come before. He lifted up the upstairs toilet and there was water around the pipe. He replaced the wax seal and caulked the empty space around it.

http://tinypic.com/r/2zdyhjm/9

http://tinypic.com/r/23rmja9/9

The issue didn't go away and I had another contractor come. He confirmed it's the toilet and said it's possible the first contractor did a bad job and if he re-seals the toilet, that will be enough. He says that might not be the source though and we have to open the wall to see what the issue is.

Judging by the pictures, is anyone here able to get an idea of what's going on? Do you think I need to open the wall? This guy said he'd open the wall and do an inspection for $200. That's not counting actually repairing it and he said I'd need to hire someone else to repair the drywall once the water issue is fixed. Does that sound right or should I be able to find someone who can quote me more precisely and do the entire job, drywall included?

[Art Maydan]

Thank you for the replies.

@Dale Walker 

It's not leaking constantly. It seems to leak when the toilet flushes. When you stand by the damaged wall while the toilet flushes, you can hear that the pipe is right there.

@Dan D.

There's no water around the toilet and the toilet is caulked down.

Do the three symmetrical, linear water spots tell you anything? It looks like something carrying water with equidistant seals or whatever is leaking. If it's just leaking at the source, how can it form those types of marks?

The contractor wasn't able to quote me the actual work. He said he wouldn't know until he sees the problem. Is that normal? I think I want someone else to come look at it. $200 to open up a wall is crazy. Does anyone have a recommendation for a plumber in Chicago?