I also use my lead on a professional basis
You could look at it this way;
Genuine
Vas 5051b - £12000 new, now £4000-8000 if you can find one second hand
Vas 6150/60 - £5000 new
Vas 5054 - £1000 new (genuine) + laptop £500 for arguments sake
Vas 5052 - £500-£1000 (now obsolete)
Updates for the above are £75 per brand per month
Tech
help is only available with a GEKO licence
Autologic with VAG licence - £6000
Updates are £800 per year which includes tech advice
Arbrites commander - £5200 with VAG licences
Free updates and tech advice for the original purchaser
VCDS - £250-300 new
Free updates & advice wether its new, second hand etc and with thourough knowledge it'll do almost everything the above equipment will.
As big rich has aptly put it there's is no issue with you buying a clone unit to make the mirrors fold in when you lock the car or knock a few fault lights out but in the professional market if something goes wrong you need to have faith in the product and count on the back up provided.
So in retrospect £300 won't break the bank and is far from a rip off for what you get.