I've upgraded my Pixel XL every year from the 6 to the 9 (pro). Say what you will about that financial decision. Each year I've told myself I only did it because it was such a "great deal" either for the sale price on the pixel or the "boosted trade-in value" from the previous.
I thought it would be fun to look at the prices for each in the context of the others and see how they varied from year to year.
Each year I bought the XL model with the lowest storage space (except the 9 pro), and pro when it was offered. Only one of the years I received a promotional item and I'll note that. The total price is listed with tax.
Pixel 6 Pro 128gb
10/19/2021
Total: $969
Trade-in: $175 (of two year old Pixel 4XL)
Pixel Buds A: $99 (retail)
Net: $695
Pixel 7 Pro 128gb
11/7/2022
Total: $968
Trade-in: $500
Net: $468
Pixel 8 Pro 128gb
12/26/2023
Total $753
Trade-in: $315
Net: $438
Pixel 9 Pro 256gb
11/6/2024
Total: $904 (with "gold" play points discount)
Trade-in: $699
Net: $205
Net (If I had bought the 128gb): ~$105
Originally I'd planned to keep my 8 pro another year, but looking at it this way it makes more sense why I couldn't help myself and go with the update again.
On another note, I find it annoying the way Google plays around with "boosted trade-in values." I get that they do a lot of sales to encourage purchases, but changing around the trade-in values to create a sense of urgency and price confusion -- especially on their own phones! -- seems distasteful to me. They should stick with what they think is the actual value of their phones, and admit whether they do or don't hold that value over time.
I got the 9 Pro XL for €330 and I'll sell my 6 Pro for around €200. Your journey is wild.