I think the Schicks are cheap for what they are, $1 each? *shrug* You can find the quattro packs really cheap sometimes.
Here's the big reason to get a proglide if you have a fusion: The blades are $9 for 3 at walmart, vs $12+ for 3 fusion blades. I saw a deal at target, buy 2 packs for $9 each and get a $5 gift card.
It has a really bright blue LED power light too. Doubles as a noisy flash light.

But yea, if you're already used to paying this much $$ for a gadgety shaver, you might as well upgrade since you can buy the shaver itself very cheap, even free in some cases.
Comes down to pricing though. Here's what I think about that; assuming you can live out 2 weeks per cartridge/shaver:
xtreme 3 disposable: $1-$1.10 for 2 weeks
proglide: $3-4 for 2 weeks
I mean it's $78 over the course of a year vs $26.
Here's a funny thought. if you used 1 full double roll of angel soft toilet paper a day (which goes for 4-5.50 per pack of 12 double rolls), then..
you use approximately 31 packages of toilet paper a year. At the price of $6 (not unusual when not on sale), that's $186 in toilet paper a year (not including tax).
At $4 (at walmart), it's $124 a year.
Funny stuff to think about eh? You're Mac users, buying food from little tiny organic shops and drinking coffee at starbucks. i doubt you care about an extra $50 a year to shave.
But I bet a lot of Mac users here buy their stuff at a shaving shop and pay $50/month for it.