Thanks for putting in the rest of the sentence - it makes analysis possible.
Leaving out the word 'paid' leaves us with the sentence
The average bundle price was a little over $8.
Here, it is obvious that the subject is 'The average bundle price'. There follows a copular structure; the verb involved is be ('was').
A 'bundle price' is a collocation possibly best regarded as a compound noun:
"...savings based on comparison of Bundle price with price of same services sold separately. ..." (Google)
and 'average' is an adjective in attributive position (actually a rather difficult type of adjective to classify - but that's not germane here).
Putting 'paid' back into the reduced sentence, it is seen to be relating to the noun group ('bundle price'); if we had 'paid by the people in the showroom' we would see it is an adjectival non-finite clause postmodifying the noun group. The shorter version 'paid' is syntactically the same.