My thoughts are that one compensates for the other.
Most musicians are not rich and so the manufactures make a loss on their synths, to get musicians to buy them, which means as most play live the manufacture gets free advertising.
Arrangers are mainly bought by the General Public who usually have more disposable income, and so manufactures inflate the prices.
When the 2 come together the profits on the arranger compensates for the loss on the synth.
As I mentioned at the beginning these are just my thoughts, and are not based on anything specific.

Bill