There is a great interest in building a beacon at the absolute minimum weight. This makes sense as the less the weight, the higher the balloon will float and the more likely it will be above the weather. If the beacon is made too fragile, then the likelyhood of failure increases. It is a judgement call about the weights of each and every component.
Consider the weights involved in flying an SBS-13 balloon.
Weight of the balloon 105 grams
Weight of the beacon, antenna, solar panels, and harness 15 grams
Weight of hydrogen to provide 6.5 grams of lift 10 grams
Total 130 grams
The electronics will weight in the range of 5 or 6 grams and maybe even a little less. Reducing the weight by a half gram by using smaller antenna wire will have very little impact on the float altitude and no bearing on the life of the balloon. The float spreadsheet predicts about 100 feet lower for a half gram. If the wire is broken during launch or fails in flight, the flight is lost.
If the balloon is to be inflated with helium, the total gas weight will be about 20.5 grams. The balloon now weight about 10 grams more. The equilibrium float will go down about 1,600 feet.
The weight can be reduced by trimming excess plastic, shortening the harness, finding the lightest foam to use for support, lightest solar panels, and so on. All of this adds up and is important to consider. The total weight and float altitude of the clear chinese balloons is a little different but the considerations are the same.