Lets say if Diff is 100,000,000 in 90 days, which I doubt it will be that High(My Estimate is 100,000,000 by Nov 2013)
At 100,000,000 My 4 7 MH will get about $480 per month... I can live with that.. But yes it is a gamble and cutting it close..
Congrats to all those who took a chance and ordered last June.. They and doing real well right now..
Are you sure you did the math right? Using the calculator http://coinish.com/calc I get $3.09 (0.028BTC) per day at diff 100,000,000 for 5.5GHash/sec Jalapeno (ref https://bitcointalksearch.org/topic/jalapeno-raspberry-pi-36-watts-delicious-227101 which is a nice post). That's a lot less than $480 per month. Don't forget to play with expert mode to see the effect of difficulty rise on ROI.
I agree with your last point, the early orders will make a killing, just not anyone ordering today.
[Edit]Or maybe you meant to say you've ordered four BFL 7GHash/sec (the upgrades). That would be about right for $480/month (but you'' still need to account for difficulty rise in ROI calculation). How much did you pay for them?