Here's when various HP terminals were introduced,
and when they were discontinued, along with their prices:

...sorted by date (and model number within date):

   Model | 1979     1980    1981    1982     1983  1984    1985  Notes
   ------|-----------------------------------------------------  --------------------
   2640B | $2600   $2600       x       x        x      x      x
   2640C | $4250   $4250       x       x        x      x      x  Cyrillic
   2641A | $4100   $4100       x       x        x      x      x  APL
   2645A | $3500   $3500   $3500   $3995    $4550  $4600      x
   2645K | $4000   $4000       x       x        x      x      x  Katakana
   2645N | $3750   $3750       x       x        x      x      x  Danish/Norwegian
   2645R | $4350   $4350       x       x        x      x      x  Arabic
   2645S | $3750   $3750       x       x        x      x      x  Swedish/Finnish
   2647A | $8300   $8300       x       x        x      x      x  b&w graphics, BASIC
   2648A | $5500   $5500   $5950   $6530        x      x      x  b&w graphics
   2649A | $2150   $2150   $2150       x        x      x      x
  13290B | $6950   $6950   $6950       x        x      x      x  2648A + more
   2621A |         $1450   $1595       x        x      x      x
   2621P |         $2550   $2650   $2750        x      x      x  integral thermal printer
   2626A |             -   $3950   $4150    $4350  $4400  $4900
   2642A |             -      ??   $6750        x      x      x
   2647F |             -   $8950   $9400    $9950  $9950      x  b&w graphics, BASIC
   2649I |             -   $7750       x        x      x      x  2649A - graphics
   2382A |             -       -   $1700    $1700  $1720      x  codename "shadow"
   2622A |             -       -   $2075    $2175  $2210      x
   2623A |             -       -   $3750    $3750  $3250  $3250  b&w graphics
   2624B |             -       -   $2890    $3000  $3035  $3035
   2621B |             -       -       -    $1595  $1295      x
   2627A |             -       -       -        -  $5975  $5975  color graphics
   2392A |             -       -       -        -      -  $1295
   2625A |             -       -       -        -      -  $3495  dual, opt graphics
   2628A |             -       -       -        -      -  $3195  HPWORD


... sorted by model number:


   Model |  1980    1981    1982     1983  1984    1985  Notes
   ------|---------------------------------------------  --------------------
   2382A |             -       -   $1700    $1700  $1720      x  codename "shadow"
   2392A |             -       -       -        -      -  $1295
   2621A | $1450   $1450   $1595       x        x      x      x
   2621B |             -       -       -    $1595  $1295      x
   2621P | $2550   $2550   $2650   $2750        x      x      x  integral thermal printer
   2622A |             -       -   $2075    $2175  $2210      x
   2623A |             -       -   $3750    $3750  $3250  $3250  b&w graphics
   2624B |             -       -   $2890    $3000  $3035  $3035
   2625A |             -       -       -        -      -  $3495  dual, opt graphics
   2626A |             -   $3950   $4150    $4350  $4400  $4900
   2627A |             -       -       -        -  $5975  $5975  color graphics
   2628A |             -       -       -        -      -  $3195  HPWORD
   2640B | $2600   $2600       x       x        x      x      x
   2640C | $4250   $4250       x       x        x      x      x  Cyrillic
   2641A | $4100   $4100       x       x        x      x      x  APL
   2642A |             -      ??   $6750        x      x      x
   2645A | $3500   $3500   $3500   $3995    $4550  $4600      x
   2645K | $4000   $4000       x       x        x      x      x  Katakana
   2645N | $3750   $3750       x       x        x      x      x  Danish/Norwegian
   2645R | $4350   $4350       x       x        x      x      x  Arabic
   2645S | $3750   $3750       x       x        x      x      x  Swedish/Finnish
   2647A | $8300   $8300       x       x        x      x      x  b&w graphics, BASIC
   2647F |             -   $8950   $9400    $9950  $9950      x  b&w graphics, BASIC
   2648A | $5500   $5500   $5950   $6530        x      x      x  b&w graphics
   2649A | $2150   $2150   $2150       x        x      x      x
   2649I |             -   $7750       x        x      x      x  2649A - graphics
  13290B | $6950   $6950   $6950       x        x      x      x  2648A + more

Note: the 2642A is in the 1981 catalog, but without a price.

Model/price information based on entries in the yearly "HP Test &
Measurement Catalog".  Thus, the granularity is a single year.
(prices don't include cartridge tape ($1600 extra)/ floppy drives,
where available)
(I didn't check for discontinuance of any terminal past 1985.)

In 1985 , HP suddenly realized how important computers were,
so they were moved to the front of the T&M catalog!

Personal Computer Notes:

   HP 125, HP 120       Introduced in 1984.   gone by 1985
   HP 150, HP 110       Introduced in 1985.   gone by 1988

HP 300 note:

   gone by 1983