My personal view after hunting all versions, it depends, if you are looking for a Bubble Strip then all 3x have the same value depending on whether they have a Frosted or Clear Bubble Strip, the value would then increase for the Blue/Teal PCB Boards and further increase for Red LED.
Lowest to Highest Value based on rarity & prop components.
Frosted Bubble Strip
Clear Bubble Strip
Blue/Teal PCB Board
Red LED
If the calculators are only wanted as a display piece then I think the EX19/20's have similar value as there seems to be a regular supply of both on evilbay with the Ti2000 possibly having a higher value to complete a display set as they are rarer.