Thanks very much to Lysander for the Humble Bundle offer
As mentioned in the above offer, you can get Vegas Pro 15 Edit for $25USD with Humble Bundle.
Then, there is currently a sale on Vegas Pro 16 Edit upgrade, for $199 AUD (down from $400), so purchasing 15 from Humble Bundle then upgrading theoretically is a great upgrade path for those who want the latest version.
Buying outright is currently on sale for $400, down from $700.
Also, unsure about cross-grading, but it could be possible to get Vegas Pro Suite for $406 (down from $1099), or Pro 16 for $263 (down from $799).
Perhaps someone in the comments can shed some light on whether this is possible - I couldn't find any information on this myself.
VEGAS Pro is different from VEGAS Pro EDIT