anyone know approx cost?

[CycloneX]

To fix a 2007 iMac G5 with the lines on the screen, won't boot, etc. I assume its the bad capacitors known for that model so a new motherboard. Given that it's an old model I was hoping the cost for the parts might be cheaper.

 

[Cox Orange]

Go to Ebay, use a serach term and choose "computers" (or whatever the category is called), then click search.
Now scroll down an look to the left. Click on ended auctions. (even, if you do not see a running auction before. Maybe no such auction is running at the moment, but was running in the last 30days).
Then sort by "lowest to highest". Green prices were sold items and red werde not sold.

From my experience every buy it now auction is not worth it and cost nearly the same as a working iMac. If you have time to wait for an auction you may end up cheaper. You can also buy a complete, but defective iMac (that of course should not have the same defects). Then sell parts and get your invested money back or make a little bit plus. Keep the part you need for yourself, of course

Did you try connecting a second display to it? If that shows a picture, it is not the capacitors, but the screen.

PS: are you sure it is a iMac G5 or are you sure it is from 2007, both won't go together.