That's a good point and it brings to mind other reasons people mention what they pay for something.
I can't speak for your friend.
Here a a few reasons I noticed that some will mention the low cost of something.
A. Their preacher preached on
I Timothy 6. They are expressing their contentment with modest means.
5Perverse disputings of men of corrupt minds, and destitute of the truth, supposing that gain is godliness: from such withdraw thyself. 6But godliness with contentment is great gain. 7For we brought nothing into this world, and it is certain we can carry nothing out. 8And having food and raiment let us be therewith content.
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B. They are expressing modesty in their speech with that which comes from their heart. The purchase was certainly something they liked and enjoy enough to wear. However, the cost was insignificant. It was in line with another verse in I Timothy...
9In like manner also, that women adorn themselves in modest apparel, with shamefacedness and sobriety; not with broided hair, or gold, or pearls, or costly array; 10 But (which becometh women professing godliness) with good works.
C. Some People don't wish to brag, but also don't want to express dishonesty of mean$. They do not glory in the riches or brag of what they spend on self.
After all,
every good gift and every perfect gift is from the Lord and comes down from the Father of lights. James
Example.
I've suffered serious injuries to my health, acute and chronic.
I Avoid drug pushers on the streets as well as those in palaces/hospitals that masquerade as "health" and "care".
The Lord in my Great Physician! Praise to God! He alone deserves all the credit despite the fact that rubs the fur of some the wrong way.
I spoke to Him about needing quality supplements that are from the things that He made.
His local people are not giving at all for the labor I've provided them since last Fall.
The Lord showed His love by putting the exact supplements on clearance $2-$3 each in my path exactly when I went to the grocery store. They were fresh and highest quality they stock.
I feel so much better now as the brain fog is lifting, I'm finally getting improved sleep, my heart challenges are improving, inflammation has dropped!
There are not any drugs in the world that do all that! Plus there are no toxic effects. Jesus made what went into those, the
Holy Spirit provided me knowledge of what I needed and the Father provided them at an affordable price!
Why would I bring this up?
...So others may benefit by growing in faith in the Lord rather than in idols

they trust their lives to.
..So we all may share in the knowledge that He provides His servant, not only in the word but also in His physical creation.
....So that God gets paid the respect due to Him alone.