While I know that this is a troll, the serious answer is that you won’t be able to train above 5m SP as an Alpha, and since you need 5.5m to extract, you will have to sub those accounts in one way or another. So you won’t be paying just the cost of the extractors. At that point, you might as well sell PLEX, and pay the roughly 25-30% premium over creating your own SP farm just to not have to wait so long. Here are the costs in terms of injectors:
000-005m SP: 10 injectors
005-050m SP: 112.5 injectors
050-080m SP: 100 injectors
080-250m SP: 2266.67 injectors
So you’ll need about 2,500 injectors to get to 250m SP. At 1.75 injectors per 500 PLEX (assuming you convert the PLEX to ISK, and then spend the ISK on injectors), you will need 735,300 PLEX total. If you buy the 15,400 PLEX packages for $500, then you’ll be spending $23,875 total. As mentioned before, you can shave off a few thousand bucks if you start your own SP farm, because subscriptions cost less than PLEX. But then you will have to wait (how long depends on how big the farm is).
But I have very good news for you! You don’t actually need 250m SP, because you will run out of combat-relevant skills to train way before that. You can max out subcaps, with the exception of some fringe support skills and weapon specialty skills to 5 (you can have a few, though), at around 100m SP. You can max out capital support skills and a single race of your choosing in another 30-40m SP.
All for the price of a gently-used Toyota.
Here’s the kicker for everyone else, though: we’ve all spent close to that much to get our high-SP characters. The difference is that we paid bit by bit, so we didn’t really notice. But a character being trained for a decade does cost thousands of dollars.
So if the OP really wants a high-SP character and is willing to pay, it’s probably not the stupidest idea, assuming he has the cash, and considering that time is money. The only real issue here is that most of the expenditure will be lost to injection taxes. So it’s probably a better idea to just buy a character on the bazaar instead.