Here's the way Disney likes it:
Buy your MYW tickets now. (Disney gets $ now, let's say $300/ticket)
But before you travel, Disney raises ticket prices. (Say they go up $20) but your existing tickets are still valid.
Now Disney likes getting even more money later, too

So after using your MYW tickets to enter a park (very important step) you can upgrade within 14 days of 1st use. Disney guest relations will then take your current used ticket, bridge that used $300 ticket to a current $320 MYW ticket and then you can use that $320 value ticket towards a $420
DVC AP.
In total you spent $400 ($300 +$100) for a $420 AP.
Now you can get even greater savings if you bought that "$300" MYW ticket from a discounter like
UT and only spend,say, $280 then you only spend $380 ($280+100) for a DVC AP. Or if there is no ticket price increase, you still get that $20 UT savings.
There are a few catches, you would not get money back if you spent $450 on a 10 day NE MYW ticket and "upgraded" to an AP. Your upgraded AP will have a start date = to the day you first used your MYW, not the date you buy the upgrade. And water park days on a MYW ticket complicate things (if upgrading to a normal AP) so read through CF's outstanding ticketing FAQ I linked above.