imagine this,if you made logo for company and that company going bigger,and company only paid you on $10 (on forum).
are you still happy?
they made $1billion/year.are you still satiesfied?
maybe any article review about that company and said 'x company make $1b per year and paid cheap for awesome logo'(like twitter)
what will you do?
i'm pretty sure you will got bad critism for another designer.
you didn't get me bro.. i meant like the $10 logos is for small buisness like for example forum threads... if the company grows by the time then you can upgrade the logo ofcourse, also i think that logos made for twitter and amazon costs some hundreds...