3.1M portfolio turned into 4.5M in an instant

My strategy is a little different than most (I reckon): I have small portfolio (only 2 properties, one is PPoR), but both are of high value currently (vs the cost of purchase) and predicted future value (based on the assumption land holds value).

I came into property investment mainly cause I'm too lazy to learn how to trade stocks, and I'm really not into anything even remotely close to day trading.
Property for me is a very stable, low risk / moderate gain asset.

I also have an internal desire to own land. On the big-ish size. Not sure why.

First came the PPoR, sits on a flat acre in what is now becoming very sought after East Melbourne hilly area.
Purchased at 2009, costing 550K, was well priced for the time (not too cheap, but definitely not expensive).
Valued today at 1.5M - 1.6M at least. Mainly due to the size of the land and the fact it's flat (very rare around here) and the size of the house, it's age and open plan design.

Then came the boring "must have" IP in Berwick VIC.
Purchased at 2012, while I was overseas. Located in a good area of Berwick. Purchased 405K back then.
Sold on 2020 (middle of COVID) for 730K after massive 130K reno.
Nothing special about this property. It was so boring - I hated it!

It was sold in order to buy the most exciting property I could dream about;
a 15HA property, with 60' house on it, 2 huge machinery sheds and gentle sloped farm land (all useable, no bush) near a township that grows steadily, about 50km from Melbourne CBD (semi rural).
We snatched the property from the market before is was advertised (agent brought us to inspect before he even took pictures nor had section 32).
Very quick negotiation (took 1 day) saw us scoring it for 1.18M.

Back when we bought it, we didn't realise what we're buying. It took us some time to understand the huge potential.
Took over the property close to the end of 2020, so about 1.5 years ago.

Since then we managed to get bad tenants out, spent 130K on renovation to bring a 60' scruffy property to the current century.

Currently it's rented for $1,050 PW (4.62% yield), and it's positively geared with 80% LVR.
In 4 years, a change in the land contract will make it $1,500 PW (6.6% yield) and highly positively geared.

But that's not the good part....
Until a week ago, I've estimate my portfolio as 3.1M for both houses (1.5M + 1.6M), with less then half debt.
But then a call came in with an offer of 2.2M right here right now. That makes the portfolio 3.7M (the caller is legit and CAN put the money on the table).
A bit of looking around made it clear that anything in the area, with similar size and similar facilities (mainly attracting the same rent) would cost at least 3M.

I decline the offer and said I'm not interested in negotiation. I wanna hold on to this property. It's not worth selling.
There's also a chance for re-zoning (even 30-40 years down the track) which is winning the jackpot, but I'm not holding my breath. If it happens - it happens.
If not - it'll still going to be prime land for rich life style with it's location, views and size.

I always wonder my strategy of holding expensive / unique properties is better then cheap / multiply / volume holding.
For me, buying those properties is more than just IP, but also fulfilling desires I had.