I can tell you how I ran Rinse It (currently on hiatus, but hoping to make a comeback).
I had an ally in London at the time (Jodie at Diffusion PR) who would get shipments sent to her by the labels and artists. Then, when enough got there to make it financially feasible to ship in bulk, I drop shipped them over to Canada.
The cost to the DJ in the end, after everything was approximatley $4-5 US per plate including all shipping handling packaging, etc.
There were usually 10-20 plates in each sporadic shipment. Plus CDs, Magazines, stickers, etc.
In retrospect, it was a lot of work to create the website and quasi-infrastructure. The DJs needed to be more forthcoming with feedback and charts and the labels were difficult to deal with from a distance. We had online feedback forms built, but even with that ease, it was hard to get the DJs to all submit on time...creating MORE lag between shipments.
That said, mad props to Social Circles, DnD, LD Cats, Ammunition, Hotflush and a few others that were stalwarts. In order for me to get the grime crew involved, I would have had to travel over - something I couldn't do with a child on the way. The majority of my contacts are from the heyday of UK Garage - Sticky, DND, Karl Brown, etc. and I couldn't go back to make friendly with the new school of the scene.
other problems included lag time - in order for it to be cost effective to ship, we'd often have to wait a few weeks to make the order big enough...and by then you could have bought things for about 2-4 x the price, but got it "when it was hot".
And of course, as with any pool, you take what you get. Yes, we got a few great tunes (like Bounce - My Philosophy before release) but a large amount was test material and filler...which is what happens in all pools to be totally candid. We also started working with some of the breaks labels like Rat due to contacts, but the majority of the pool DJs appreciated more of the "pure" garage.
I'd still be willing to work on something, but would definitely need some help. And maybe make it more digitally based with encrypted files? I dunno.
Shipping of vinyl is costly. We figured that if the DJs ate most of the cost that the labels would jump on the chance to get it played in the US and Canada. Some labels/artists supported that and actually got a fair deal of airtime over here if you check some college charts, playlists, etc.
Also, I hear a lot of the labels saying how they can't give out any promos without cutting into their ability to break even/make a next record and are thus unwilling to give out any, especially to the US, Canada etc. where they can't even guarantee they get played to people vs. bedroom.
BTW, for those of you interested in a pool, the purpose of any pool is to get material into the hands of DJs that actually play out, have radio shows, contribute to charts, review for magazines, etc. i.e. you have to do something that could potentially promote the music to be in a pool.