[Highroller86]

You probably know this...
You've done a couple runs, got some serious Nuyen and now you want to
turn said Nuyen into some new gear...
But!
There is availability...
So from what i've learned (and... Please DO correct me if i am wrong at any point)
your desired object has a certain rating. Let's take the Platelet Factories Bioware for example.
Those have an availability of 12 (cuz who uses standard ware, huh?)...
Now let's just assume you called you fixer and asked him if he/she could get a hold of someone
who could sell and install this little cutie for you...
The fixer in my example has a connection rating of 5 and the charisma and negotiation from the examples in the core rules... (5 & 9)
Because my character really WANTS this piece of Bioware, he throws in another 20400 Nuyen, which will provide a dice pool bonus of 4.
The fixer knows that the item his client requests will help the runner better survive the jobs he does for him and also,
he did a valuable deed for his employer in the last run, so the fixer is willing to really let his skills get to work!
(The GM decides that the fixer uses a point of edge for the "push the limit" option)

And here it gets a bit confusing...
The GM rolls 5 (for charisma), +9 (for negotiation), +5 (for connection rating), +4 (for extra nuyen), +5 (for edge), = 28 dice.
He scores only 10 hits, but thanks to the usage of edge here, he can roll the 6es he had once more which just barely brings him to
the desired 12... So in this example, i WOULD get the bioware, but i'd have to wait 2 weeks instead of 1.

Is this all correct so far?
Also: Would i have to pay the extra Nuyen even if the negotiation test failed?

[Jack_Spade]

You forgot that the Availability is an opposed dice pool as well. So the 12 are the dice not the successes.
For downtime purchases I personally just buy successes for Avail. so you'd have to beat a threshold of 3.

[Highroller86]

Meaning that the 14 btw, it's 12+2 for alpha, could just as well result in only like... ~5 hits that i'd have to beat?
Phew... THAT'S a big relief! I just saw the availability for the suprathyroid gland and was like... "Drek... Never gonna get that..."

[kyoto kid]

...that's sort of the way it's done in missions as well. with the difference being the contact's pool is (2 x Connection) + Loyalty.

For ,example my Adept has Dr Benjamin Tate (one of the Missions contacts you can earn during play) at a Loyalty of 3 so he would have an effective pool of 13 divided by 4 (round down) for three purchased hits.  that would be enough to get any ware up to 15 availability (as it's "pool" would also round down).  If my character is looking at something that's an availability of 16, she would have to add 75% to the cost  (adding three dice to the pool).

If your character is going to be frequently looking for a specific category of hard to get gear (like my character Leela who is a demolitions expert), there is the Underground Pipeline quality which adds +2 to the contact's dice pool.  This is especially helpful when using the purchased hits option.