I have ~ $4000 wrapped up in a compressor. This includes an additional filter tower, whips, fittings, gauges, etc. It's run from a 1 cylinder diesel engine. I've pumped somwhere around ~ 60+ tanks so far, or around 5000cf. It's been up and running since March? of this year? We have 6 divers in the family and I try to dive as often as I can.
I'm not sure that I'll ever "recoup" what I've spent, but for me driving 45 min 1 way, paying $12 / tank for air or $17 / nitrox, it's worked out. Being able to blend my own nitrox has been huge for me (not to meantion I don't have to drop tanks off which turns a 1.5 hr trip into a 3 hr trip). If I went diving with 2 sets of doubles the dive was $68 just for gas alone. With a compressor and mixing my own nitrox it's like $5 for both sets of doubles and ~ 45m-1h min personal time to fill them. And God forbid the dive gets blown out, I really don't feel bad diving in a quarry with what would otherwise be "expensive" gas. If I was to factor in the fills and nitrox fills and the driving back and forth I think I've saved around $1000-$1200, and a good bit of personal time driving / dropping off.
You could also look at that as I've paid ~ $66.66 / fill this year
($4000 / 60 fills).
Also, if I do a short dive and breath a tank down ~ 1000psi, it's really not a big deal to pump back up. That always seemed to sting a little more going to the lds knowing that even though I only needed ~ 50+ cf of gas (in a set of doubles), it was still going to be $24.
Also, also, did I meantion that I never have to leave the shop with short fills? As a matter of fact, I turn LP85's into ~ 105's and HP100's into 114's. I never, ever have a short fill. That alone is almost worth buying a compressor to me.
I can honestly say that owning a compressor has gotten me to dive more than I would have otherwise. Sometimes logistics for me means I just couldn't dive because I didn't have time to get fills. I do have time to wake up at 4am and fill tanks, and I can do that any day of the week.
One last thing is if I ever wanted to sell it I'm pretty confident at the very minimum I could break even.
I don't know, just my 2 cents... if it ever breaks, I 100% will be on here crying how dumb I was for buying a compressor