Well, you will get credit for what you paid for the 3 day ParkHopper, the common price is $169 for the advance purchase version, but the ParkHopper is coded with the price paid.
You are allowed to take that amount and apply it to any Annual Passport that is equal or a higher value.
So, if you live in Southern California, you can just "trade" the ParkHopper for the Southern California AP, since it is $169.
If you want the Deluxe, it would currently be $90 more, that you pay at the AP Processing Center (the Bank of Main Street) when you upgrade. Now, this is based on the current price, if AP prices goes up, then you will have to pay the higher price.
The key is that you get full credit for the price paid for the 3 day ParkHopper on any of the 3 days of use, so you can use the 3 days to avoid Blockout days, and then on the last day, upgrade to an AP.
Last year we upgraded our 3 days park hopper tickets to AP's. The weird thing is, the difference we had to pay was like $50 each for the So. Cal AP, which meant our hopper tickets must have been pretty well priced. (the So. Cal AP's are only like $160 or around there). We were on a vacation package though, maybe that had something to do with the low ticket price.
Just don't forget to buy it before you leave. Our friends thought they could come back with their used Hopper ticket (2 days later) and they wouldn't accept it for credit. It took some wrangling to get them to make an "exception."
Also, Disney used to accept multiple tickets for credit toward APs, but they have changed to only accepting one. At my events, I routinely give away Disney tickets to my attendees and some of them would come to multiple events and collect 2 or 3 until they had enough tickets (unused) to exchange for an AP. Disney now only allows one ticket credit (unless you have a corporate contact who can help you out).
We did this very thing last year. We actually live in Indiana and only get out there once a year. But for some unavoidable reason we were out there later than usual last year (in August). We knew we'd be out there in May/June this year, so we upgraded to AP's. Worked out great. We actually did it BEFORE ours expired---midway through the trip. Since we got the Deluxe version, there was maybe only one blackout date---Saturday I think.
Anyway, we used our AP's the rest of the trip for discounts in the park (10% off most eateries---and at Disney prices, this adds up!!)
Then this spring we returned to Disneyland and it was so nice not to have to pay for park hopper passes since we had our AP's.
Last summer I purchased two 5-day park hoppers for $200. (I plead the 5th on where or how I came by these tickets) Then I traded them in for 2 Deluxe APs. The retail value was $189, so I got my AP for $50 each. All in total, I paid $300 for 2 AP deluxe passes. I have made 5 multi-day trips since. My last trip will be next week. Hmmmm...let's see, 16 days at Disneyland for $380 (We paid for 1 blackout day)?? Tha's just 23.75 for admission each day. Yeah. I'm going to say--WORTH IT!!!
To All Who Come to this Happy Place.... Welcome! Disneyland is Your Land!