I’ve been looking at the two watches (as well as the Speedy) and I’m still confused why the SeaMaster 300 is more expensive than the 300M Diver? They both appear to be Master Chronometers, indeed the difference seems to be that the 300 is more ‘heritage’ and 300M Diver possibly more common.

The current difference is:
SeaMaster 300 - $9,435
SeaMaster 300M Diver- $7,900

What gives?

 

One difference (that still won’t justify the price difference) is that the Seamaster 300 uses LiquidMetal for the numbers in the bezel, while the 300m uses paint. The bezel markings on the 300 should theoretically last forever, while those on the 300m may fade over time and possible chip.

With that said, it really comes down to marketing. The Seamaster 300 was introduced when the older 300m was still in production and using the 2500 co-axial caliber (which had the co-axial escapement added to an older existing ETA-based movement). Omega priced the Seamaster 300 with its improved antimagnetic in-house movement at a significantly higher price (justifiably). When the new Seamaster 300m came out with its improved antimagnetic in-house movement in 2018, Omega decided not to increase the price significantly over the price of the older 300m. I forget the exact increase, but it was on the order of $500-750. Omega could have chosen to bump up the price even more, but I suspect they wanted to keep it lower to push up its popularity.

That seems to have worked.

 

The previous SMPc was $4400 on bracelet. So the new model increased by $500 on rubber and $800 for the bracelet.

 

If you're looking for logic in the pricing of luxury goods you should spare yourself the effort. It's not a business in which value for money is a thing.

 

The price difference between these Seamaster lines tends to flatten in the preowned market, if you go that route.

 

You’re right on this side, a reseller has one for a $2,000 price drop only a few months old (not sure why someone sells a 3 month old watch) but it flattens the curve between the 2 watches.