You fail to include wordpress, anyhow Joomla is what I most prefer because of it flexibility. It can be very pain in the ass at first but after sometimes you will love it because of its flexibility and features.
Joomla is an open source, no cost to spare at all,buying a template would cost around 30$ to 50$ depends, if its a company template but if its listing or directory website it will cost around 99$ to hundred not included the extension which majority you can use the free one.
If you compare os commerce, wordpress and magento, of course magento would be more stable and professional. You will need more powerful hosting for magento, but other than that it's same expenses in future. I saw a private sale solution, developed by Plumrocket company. I think you can find it on their site. Its basically a package of magento extensions and magento private sales theme. You can also extend it with cart reservation, magento invite friends functionality with ability to import address book and magento reward points extension. If you really like Fab.com or Gilt.com you can add some magento social shopping extensions such as live feed plugin, inspiration wall, faves… etc.
Choosing the right CMS will really depend on your overall goals. Take a moment and think about what you plan to accomplish with the site in 5 years from now. Jumping into one CMS without any research on the others is a fatal move. You don't want to spend months, if not years building out a site, then come to find out that a small pivot in your business now requires you to rebuild the entire system on a new CMS.
Just about every open source CMS software provides a membership function. That's easy. It really comes down to how complex your site will become. Don't think tomorrow, always think 5 years ahead.
wordpress.org is great for plugin and go, so is drupal.org, but Drupal can get very complex, very fast if you get too carried away with new features. Drupal is great if you know a little about development and have people around to give a helping hand.
Possibilities are virtually endless with Drupal so as long as you use it correctly. You can really scale with Drupal in ways you probably can't even imagine. This is a nice fall safe in knowing you have the right CMS.
Let's not forget Drupal's new version, Drupal 8. I have personally tested and it's nice! If you think Wordpress is good, just wait. Drupal 8 is going to be so easy, even your Great Grandmother will think so.