I have played all versions (from 1.0 to 1.3) and the tech exchange is still weird.

First of all i dont need previous technologies to get future one. As an example i can get Plasma II wepons without researching Plasma I. Then i can continue to research Plasma III without ever needing to research the first one.

Second of all AI request unreasonable amount of ressources for some lower techs. As an example i can exchange Plasma Weapons for an Inpulse drive but i can not exchange it for New Propulsion Techniques. (Which is 2 grades lower).

The explanation of the second principle may come from the fact that the AI is very reluctant to give his level technology, while no minding giving away the next ones. I can exchange for Plasma II but bot for Plasma I. There is some other really odd technologies which are really hard to get like Basic Logistics and Enchanced life support. (For some really odd reasons).

The exchange price of technologies does look to depend on how many other races have it. (no to whatever there is a better technology or not). The value of laser is basicaly the same (as an exchange) whatever ther eis 1 or 8 races who have it.I can not get easily some techs (like advanced Hulls), even if all teh other races have it. Some other techs are very easily give even throught no other races pocess it (like Advanced Trade).

Finally the worst part is how the AI exchange techs. As an Example This is what got for an Ion Drive (using like 50 exchanges, getting and exchanging back the tech).

Note i never reaserched any military tech. Here what i got.
Laser up to Plasma II (with exception of Plasma I)
Basic Missile
Mass Drivers Up to Miniball II.

Defence
Up to Enchanced Deflectors.
Up to Tritum Armor.

The i also got
Logistics up to enchanced.
Minituarisation up to enchanced.
Research Academies.
Xeno Factories Construction
Planetary Invasion
Advanced Trade
Soil Enrechisment.

The Top Levels are owned almost exclusively by me and 1 or 2 other races.
The only techs i could not get are New Propulsion Techniques, Plasma I and III,Phasors,Advanced Hull Desing and MiniBall II.

The result is have the biggest technological tree while spending 0 on research !!!!.

---------------------------------
For the first part, the tech must be made dependable (no Plasma II without plasma I), while the exchange rate must be dependable for the reaserch price.
The only way i see to correct this problem is for each AI to exchange all new tech with either everyone or nobody. Or make some enable ppl to only exchange the tech they have reaserched. ( ie you can only trade plasma II if you have reaserched it. if you traded it you can use it but not use it as an exchange). From natural perspectives we can say it a non full technological transfer.