Per win boosts will give you about 145 more ip every win. Coincides with my experience when Riot gives free boosts and this source:
http://leagueoflegends.wikia.com/wiki/Boost
A 50 win ip boost costs 2560 rp. Wowza. I would be very sad if I misclicked and bought that because I am at the point I save ip for runes and champs I'll probably not use much. Anyways when the 50 win ip boost goes on sale it'll cost 1280 rp. And 50 wins with it on normal summoners rift will eventually get you 50*145... 7250 ip...... Barely enough for a full priced champion. So in other words, per win ip boost are really bad unless you really need to rush runes which honestly you should not need to because two rune sets should be fine for most champions. I only use one rune set on my smurf (AD marks, attack speed quints, and defensive seals/glyphs helps every champion somewhat)
Remember, champions go on sale for RP too. That's the better deal really, but you can't control what is on sale...
Now for duration based ip boosts...
I noticed the 4 win ip boost has the same rp cost as the 1 day ip boost. 290 rp (145 rp on sale)... So the one day ip boost is assuming you win 4 games in one day. Let's imagine you win 50% of the time. You would expect to play 8 games to break even with the not so worthwhile per win ip boosts.
Actually scratch that because I believe duration based ip boosts award you on loses too... So I would guess a 1 day ip boost is comparable to the 4 win if you play 5 or 6 games: 3 wins, 3 loses...
The 3 day ip boost is much better though. Only 60% of the cost of buying three 1 day ip boosts.
The not so good 50 win ip boost is only 70% of the cost of buying twelve and a half 4 win ip boosts.
Gonna stop here... Concluded even on sale they barely pay off despite the time commitment... Gonna make a formal thread about it later. Boosts need a massive permanent price reduction and while they're at it they should just combine EXP and IP boosts. No reason for them to be seperate these days.