A comment in another thread inspired me to do a bit of investigating into the profitability of micro transactions and here's what I came up with:

Well I did some quick and dirty number crunching and I mean QUICK and DIRTY to get an idea of profits from the market. Here's what I came up with. Let's take a look at an approximately $2.00 skin. I chose this because it was the median price of all items on the market (median is less subject to deviation then the mean but that's for a stat lesson some other time) It is a "MOSCONI 12G SHOTGUN | First Line, Broken-In". There's a median sale price on steam for each weapon. It sells for about $2.00 twice a day. Maybe $1.90 one day maybe $2.12 the next. Maybe one gets sold that day maybe 4 but it's a good enough approximation.

So $2.00 skin sold 2x per day, I only make $1.75 so $0.25 is lost to the powers that be

If I want to make $0.01 on the market I have to sell at $0.03 so lets say OVK and Valve split the profits 50/50.

Then that $0.25 lost is $0.125 to OVK/STRBRZ 2x per day. so $0.25 per day.

Now for the quick and dirty part...

At 114 pages of items at 10 items a page, Approximating the profits from all items sold at all price points averages to around this Mosconi's price point (the $100 dollar plus skins being sold once every week or less maybe and the $0.03 cent items being upwards of 30-40 times an hour) then that's 1440*$0.25=$350 profit per day or $10,500 per month.

Hope that helps, though take it with a grain of salt.

IMPORTANT- If anyone has some link to the actual split of profits by Valve and OVK/STRBRZ or any other types of real life figures please let me know and I will work it into the calculations!

Edit: I have been informed that there is likely not a 50/50 split between OVK and Valve but more like a 33/66 split in OVk's favor. Then that's now $475.20 per day and $14,256 per month.