Hi mridea,
if you have a suggestion you can post it at the new idea exchange forum
http://ideas.appthemes.com/forums/84267-classipress
You may also check the plugin repository at wordpress.org.
There are a few plugins that enable you to put a paypal button in the sidebar.
P.S. just re-read your post ... think I got it wrong the first time
There is already an option to say thank you via the thank you button.
Although it is not money I am sure one or the other will appreciate it.
Last edited by bluecafe; December 7th, 2010 at 03:36 PM.