At 1.500usd it was quite a safe gamble. At +5.000usd the expected value is negative. Unless BFL is a complete scam, and no other player delivers a single ASICs, 90btc is a losing proposal for sure.
At that price I would only buy one if I had hundreds of btc, mined/bought when the exchange rate was much lower. Which unfortunately is not the case.
You have to stop thinking in USD and think in BTC
A batch #1 Avalon cost about BTC 106 when it was paid in September 2012
The question is: how long does it take to earn back the BTC at current difficulty when the machines are delivered?
None of the Batch #1 Avalons (except the first 3) have earned back their value in BTC amount, but they are coming close (mine have earned BTC 78 each by now)
Batch #2 machines were cheaper and Batch #3 machines will be even cheaper, but difficulty will go up dramaticly. If you break even after 100 days, you can be glad. I wish my other investments broke even in 100 days and after that started generating free profit
If you want to look at the USD value, you are way better off to buy BTC and store it for 100 days, you will have a lot more 'profit' that way in USD but you will not have more BTC
What is your game? You want more USD or more BTC? Choose wisely ;-)