Eh, I kinda see what they're saying. They haven't become cheaper at all, but GPUs have increased in performance, and the amount of performance you get for each dollar spent has increased.

Relative to its siblings, things have gotten worse. A GTX 970 could hit 60% of the performance of the full Titan X at 35% of the price. A 5070 hits 40% of a full 5090 for 27% of the price. That's overall less series-relative performance you're getting, for an overall increased price, by about $100 when adjusting for inflation.

But if you have a fixed performance baseline you need to hit, as long as tech gets improving, things will eventually be cheaper for that baseline. As long as you aren't also trying to improve in a way that moves the baseline up. Which so far has been the only consistent MO of the AI industry.