If possible try and focus on increasing your ilvl first before hardcore farming neth's lair as even one extra 746 piece makes a noticeable difference in speed runs.
Did random math, sorry for long post.
*Edit: The important thing in speed runs are can you reach the instance lock-out limit, and the chest per minute speed at which you do it. If it takes you 6 minutes to get to the second boss and kill it for the second chest, when you could be doing the first chest in another 3 minutes, and you never hit the lock-out limit, getting 1 chest is better*
While I agree with your point, the faster you can kill the first boss the faster you can do speed runs (it's actually more effective to not do the second boss when the chest spawns in spot 1 or 2 on my map). I'd argue that gear for most people is gold-gated, and you are either stuck farming for yourself murlocs, or trying to get through other avenues to buy the items off the AH. My data set isn't statistically significant yet, but I've been logging the gray items I get to average out the gold from a per chest basis.
As it stands I can get the chest and be out of the instance in 3 minutes and 21 seconds on average, and this requires only killing the first boss. Each chest has as of right now (only 47 logged) a 60% to yield AP, and on average yields 61g 71s. If you are only doing single chest runs you'll average 6 AP tokens and 617g for every lockout period (aka an hour). If you are gold gated and able to do 1 chest runs at a sub 6 minute pace.
I'd argue this is a better long term strategy because sooner or later you'll get the gear you want, and then you wont need it anymore, but you'll always need more AP. You generate the gold you need for the gear, while getting the AP you'll always need. Thus the twink will pay for itself. If you have mining and enchanting you can also mine the first boss and DE any blue you get. As it stands right now I have a 42% of getting a blue off the first boss, and 1 leylight shard is another 70-100g on my server. So that same lockout period yields around another 400g. 1000g per lockout isn't great from a gold standpoint, but since you get AP from it again, you accomplish two birds with one stone. 1 lockout is essentially 10 runs, which is "half" of my daily assumptions for how many days to reach each level, but lets just take my daily assumption of 10 tokens, which is 20 chests. Data points that this is conservative estimate, but at 20 chests, you are yielding 1200g a day. To reach rank 25 is 180 days. If you plan on reaching rank 25, which is totally feasible based on the amount of time most people put into twinks. You will generate 216k gold for yourself from gray items alone. That should be more then enough to fund most twinks.
Again, if you can get gear, gear is great, but if you are strapped for money and are capable of solo'ing (or grouping if your NA alliance, cause I run this all the time and anyone is welcome to come 99-109), I wouldn't be in too much of a hurry. Prices WILL drop, and you'll be saving up a nice nest egg for buying the items you really want instead of "non-perfect" items. Again, this is my opinion, but if you are buying ilvl 835 gear as a 101 after you are capable of soloing the first and third boss this is a waste, because you could of used that money and some patience to get 850+ gear.