I know smooth just made a mod note of keeping back the discussion, but here's my numbers:
292 bytes is coinbase reward
427881 blocks total
124,941,252 bytes for total bytes for coinbase reward
3,573,000,000 is the size in bytes of the blockchain
5002 pages is the number of pages chainradar has of blocks with >1 transaction in them, 30 blocks a page
2536 @ 2 tx ea = 2526 * 30 = 75780 transactions
3617 @ 3 tx ea = 1081 * 2 * 30 = 64860
4148 @ 4 tx ea = 531 * 3 * 30 = 47790
4462 @ 5 tx ea = 314 * 4 * 30 = 37680
4666 @ 6 tx ea = 204 * 5 * 30 = 30600
4800 @ 7 tx ea = 134 * 6 * 30 = 24120
4867 @ 8 tx ea = 67 * 7 * 30 = 14070
4906 @ 9 tx ea = 39 * 8 * 30 = 9360
and add another 30000 estimated all the way until the last page
so a total of 304260 plus an estimated 30k tx's over a block with greater than 10 tx's a piece gives us a total of 334260 transactions.
So, my average monero transaction size is actually closer to 10315 bytes, more than 10x higher than your figure fluffypony.
How do we come so far apart?
Keep in mind that I'm going to put an accuracy on my figure of about 90%, but we're still so far apart.
Sorry, stopped reading when you Stated bytes were kilobytes.
Size, bytes 2561
Pretty sure this is a difference in dialect.
America: 2561 bytes = 2.561 kb = 2561 bytes / 1000 bytes/kilobyte
Wherever you are: 2.561 kb = 2561000 bytes
Where are you?
In Binaryworld kilo is 2^10 = 1024. This isn't the metric system

Please forgive me for the additional 2.4 % + .0024^2, etc ... error in my numbers then