I think I can bring this full circle:
If your friends are annoying enough that they can't pay a bit more and split the bill evenly just to simplify the process for everyone involved, here is what they can do. I can see this working especially well even if everyone is paying with a credit card.
Split the bill evenly, then add tip based on how much more your meal was, so that those with expensive meals tip more to make up for it, and those with cheap meals leave little or no tip. The wait staff gets the full tip they deserve, and everyone pays what their meal cost + tip.
Warning: Spoiler! (Click to show)
I had a pair of John Varvatos gloves bookmarked from winter collection on sale for 40% off past couple months. Yesterday I decided to purchase but they were back at full price and the link was hidden/removed from the site. I called the number on the page and the guy tells me they're no longer available and the order would be cancelled if I were to complete the purchase.
Ten minutes later I remembered you can never trust anyone getting paid minimum wage or near it so went ahead and made the purchase. Just got a shipping confirmation and tracking number for it today.