How? Because for all I (and apparently you) know the two dollar figures you mentioned could have been from different buckets. Perhaps, as previously mentioned, the $150 was low bucket and the $400 was high bucket. Being at the same time of the year has no bearing on the matter. The fact that you paid $150 for a ticket 8 years ago and $400 recently for the same ticket means little without knowing the details (buckets).
Misleading? How is a range of potential bucket prices going to trump the actual price paid for the same trip at the same time each year? My experience may be anecdotal but it's neither misleading or irrational.
On the surface that does indeed sound substantial. But such conclusions are misleading without knowing what the bucket levels were.
Over a period of about eight years routine sleeper fares I was buying for simple transportation between my two most common city pairs more than doubled from a low of around $150 to just shy of $400 each way for the dates I traveled each year.
Just how much has ticket cost increased over time? I've only got about 17 months of fare data, but a quick look at the EB and CL shows their fares went up about 2.2% during that period (or about 1.7% APR) for mid-bucket coach + roomette. Do you have anything more concrete than "substantial"?
. . .the ticket cost has substantially increased over time.
While there may be a substantial difference in the prices paid, if those prices weren't at the same bucket level they can't really be compared.
Of course they can be directly compared, do you think that the vast majority of potential customers care about buckets and what the lowest price they could have paid? Or more likely that are simply concerned about the price they are quoted at the time they want to book? If 12 months/3 years or when ever they made the same trip and now they are being quoted twice or even thrice the price then they are feeling an massive price increase and will determine if they will travel by Amtrak based on if they feel the new fare is value for money.
Not everyone has the time or interest in pouring over spreadsheets and checking amsnag to work out the changes in bucket prices etc