Why should adding an extra 2gb ram jack up the price though? Other high-end smartphones have 6gb ram and they're cheaper than the Pixel 2 XL. There should be no reason why the Pixel 3/3 XL would need to be charged at a higher RRP because it has an extra 2gb ram.
Galaxy S9+ has 6gb ram, a second camera lens, comes bundled with headphones and is cheaper RRP than the Pixel 2 XL. If the Pixel 3 XL needs the price jacked up even more than the Pixel 2 XL simply because of the addition of a little extra ram, then something is every wrong.
The 3GB in the iPhone X and 8 Plus is $25-26 per unit. The 6 GB in the S9+ is $35-40 per unit. That extra $9-15 per unit represents an upfront cash outlay of between $270 million and $4 billion dollars. They're going to pass those costs on to the consumers.
More importantly, retail pricing for devices is typically based on a ratio to the cost to manufacture. As an example, if your phone costs $300 to make each unit and your retail pricing is $750, then your ratio is 2.5:1. That 2.5:1 is being determined by bean counters and is intended to represent the expected profit margin needed to justify the product's existence. If your ratio is 2.5:1 going into modeling and at the end of the process you find out that it's going to cost $350 to make each device, rather than $300 - that extra $50 is going to be multiplied by 2.5 and now your suggested retail just went from $750 to $825. A business decision could be made to reduce the margin on the delta in order to try to drive more sales, but at a minimum they're going to include that extra $50 in the suggested retail, whether or not they choose to recoup all or part of the $25 additional.
Recently phone prices have gone up because component costs have skyrocketed. The companies have chosen to share some of the cost on that, but they have to be smart about the inclusion or exclusion of components from a value add standpoint. Is 2 GB more RAM going to sell enough additional devices to justify the cash outlay? For Pixels, it would mean fronting about $50-60 million in cash. That would require, in your scenario where the price doesn't change, that the 2 GB RAM alone be responsible for driving another 80,000 - 100,000 purchases. Is that likely? IMO, no. But they have better analytics on that then I do.