Though I own one, but I think that 4.9 buds sale is more of an outlier, that sale was rather old (though still valid under the rules), and it was sold off rather quick. That sale took place on the 7th of July, which is 1 month 23 days old, close to 2 months.

Moreover, two very recent sale already prove that:

http://www.tf2outpost.com/trade/22221265 - sold for n&b brainiac + 50 keys

http://www.tf2outpost.com/trade/22257928 - sold for 6 pure

Compared to the almost 2 month old sale at 4.9 which was sold in a day or 2. Both of these sales are definitely higher than 5.6 buds and happened in less than 3 days as well.

As mentioned above, the 2 recent sales show that 4.9 buds is too low, as both sales are definitely above 5.6 buds. I'd rather see this based off a more recent sale, rather than an old sale which is close to 2 months old.