Here's my take on it:

$2 per watt for top-quality emitters. Slight discounts for volume purchases.

Meanwell drivers are about $1 per watt. The PLN60-15 is currently $55 (I think that's what ledtime was referring to) but that'll drive 60 watts of blue leds -- that's enough for 4 Procyon eqivalents (in flowering lamps). If cost is an issue, I'd use 15W 660nm for red, and a CFL or T5 for blue. Otherwise, your blue driver's almost wasted driving just 1 or 2 blues.

I tend not to figure in costs for kick-ass heatsinks (you can use "scrap" aluminum, or copper) PC fans (gotta dozen or so layin' around) or soldering and equipment like a volt-ohm meter. Where you expense a Mastech bench supply is up to you. It's not required to build a light. But it'll let you "dial in" the leds to whatever YOU decide is the most effective way to run them. And the Mastech can double as a driver.

So, $3 per watt's still my claim. If you wanna get into building your own power supplies using LM317's or similar, those devices cost mere pennies--that's how the Chinese UFO's can be made so inexpensively. (That, and using basically obsolete, low powered leds in bought in huge quantities at steep discounts.)

You can get a 20 amp 12V supply for what, $20? (Prolly got summa dem roun' heah, too.) So, doing it that way, your power supplies can cost almost nothing. You could run a blue or two off an old wall wart with an LM317 added to regulate current. Cost just a few bucks for the whole assembly.

The Meanwells, IMO, are just too good a bargain to pass up, and you can certainly re-sell them when you're done with 'em. I'm gonna build myself some power supplies when I get a round tuit, just for fun. But I'm willing to pay for the Meanwells, even though I could build my own for less $. I think they're worth it.

Acquiring all the odds and ends you need to build the first 75-watt led light might be pretty pricey if you have no tools or scrap electronics to start with. But if you can get one going, adding onto it is simple and very cost effective.

P.S. I just retired my Procyon. It worked well enough to replace my HPS, but these 15 watt 660's are totally kicking its ass as a flowering lamp. The Procyon, remember, cost $6 per watt.