You can buy diggs but people have been banned for doing so (I believe it is against their ToS). If you're going to buy them you should do them in short bursts (20-30 per story), not buy hundreds. Either way I wouldn't recommend it.
To get listed on the homepage of Digg, you need to hundreds of digging. Do you want to buy the hundreds of digging?
That will be short term if you go for paying someone, better to have good content, there are chances that many people will digg it naturally.