I believe in the past, the once-a-year letter was to pay for the C.O's insurance. So this sounds like nothing new. It's sounding a bit high for one year. I doubt that amount actually gets sent off to some insurance company.
Here's the thing: their membership is their primary source of money. If members are squeezed for money like balloons could be squeezed for their air, there's only so much there. If members used to donate a great deal at conventions and assemblies and now have to contribute more at their local congregation to pay the bills and meet Watchtower's inflated rates for insurance, then the same members will take it out of their assembly donation money and say "I gave at the Kingdom Hall." The balloon only holds so much, especially when you don't go to college, don't work overtime very often, need time off for conventions.