From the core rulebook:
Psychic Technique
Talent Groups: See Psychic Techniques
Either through training or natural development, the Explorer
has learned an additional Psychic Technique. Once this Talent
has been selected, the Explorer may select one new Psychic
Technique in any Discipline he possesses with an xp cost
equal to or lower than the Talent’s xp cost. Note that when a
Psychic Technique is selected, the Explorer does not have to
spend more xp–he spent the required xp when he purchased
the Talent. This Talent may be chosen multiple times, each
selection granting an additional Technique.
So it's up to the Talent's XP cost. In your case it doesn't matter since it's free, but if you wanted to get an 100 XP technique with a 200 XP talent, it would still cost 200 XP.
This has been errata-ed. It has no effect on our Stropath (since he used his starting Techniques), but for future reference, this is how it works per errata:
-You get the psychic technique talent in your advancement table with a cost (let's say 300 xp); this represents the maximum xp you could pay for a power (so no 400 or 500 xp power in this case).
-You select a power with a given xp cost, that's the actual cost you pay for the talent. So in the example above, if you selected a 200 xp power, you'd only pay 200, not 300 (as it was the original rule in the book).
