A lab's just a lab. No distribution makes it very hard to do anything. Setting up a distribution network yourself takes LOTS of time. Distributing by selling on the streets yourself means a risk of getting caught and a very low time/profit ratio. You can't just tap people on their shoulders and ask them to deal for you neither, chances are that the ones who would do so are already affiliated elsewhere.
Either way, you'll be in direct competition with other gangs/mafia/Yakuza already working that region and they will bomb the lab first chance they get.
Eventually they'll also need new supplies.
So they have to make deals, and it's very likely they'll end up paying a large share of their gains to fund transportation, 'protection', suppies etc.
If they decide to go for full profitabilty, the game will stop being Shadowrun, they won't have time to do missions and probably won't get offered jobs anyways, they're just too hot to be associated with and have a bad rep.
If they want to keep running, which I assume is the case, they'll have to outsource. You as the GM decide how much profit they keep and how much they have to pay for all the rest. That's how you balance it.