In the exercise section of the chapter on potentials in my textbook, the answer to the question "kimono wo, kaimashita ka?" is given as "iie, takasugite kaemasen deshita." Unfortunately, in neither the discussion covering -te forms or potentials is the reasoning explained. Does the potential in this case necessitate the usage of "takasugite"? Also, does it forbid the use of "kara", as in "takasugite kara kaemasen deshita"
高い｛たかい｝(takai) is 'to be expensive'. To say something is too expensive, or too much of any i-adjective, we remove the final i and add すぎる (sugiru). This makes a new verb 高すぎる｛たかすぎる｝(takasugiru) which means 'to be too expensive).
Now we can manipulate this new verb just like any other verb. In particular we can change it in to the て-form to give 高すぎて｛たかすぎて}(takasugite). In its simplest interpretation て just acts like 'and', so the full sentence becomes
No, it was too expensive and I couldn't buy it.
But this 'and' implies causality just like it would in English so it is equivalent to using 'because'.
Your final suggestion "takasugite kara kaemasen deshita" doesn't make sense because "verb-te kara" mean "after doing verb" so in this case "after too expensive". You could say "takasugiru kara ..." to mean "because it is too expensive". This would have an equivalent meaning.
て can be used to concatenate some verbs in a single sentence. For example:
- 行って来ます。I go and will return.
- 食べすぎて眠くなりました。I ate too much and became sleepy.
すぎる represents over states and actions. For example:
- 食べすぎる too much eat
- 高すぎる too high
~てから is used to concatenate verbs with temporal. For example:
- 食べてから寝ます。I go to bed after eating.
If you want to say "Because the price is too high, I cannot buy it.", the proper use of から is as follows.