I have been in this same situation, but the opposite way. My site was slowly losing members and I would downgrade as time went on. Had to pay for two servers during the transition. I used unmanaged servers which are much cheaper. At my peak I was paying $60 per month back in the early 2000's for a Celeron config with a few hundred GB hard drive. Currently I am paying for an unmanaged Core 2 Duo E7400 2.80Ghz, 4 GB RAM, 500GB HD, 100mbit unmetered connection for USD $10 per month. Unmanaged meaning, if anything goes wrong, I have to fix it.
What I did to offset the cost was add Google Adsense to the site in April 2006. I am sure Mike is no stranger to it and without even looking I bet its been debated here. Ads suck, but tech has advanced so far that you are tracked more ways than one, everywhere. We're all used to ads, and I bet some of you reading already have ABP installed. Anyways, I implemented Adsense in a way that was unobtrusive yet present in areas you had to scroll through. Tech savvy users could block it, but the vast majority of visitors seen it. To date (25 Apr 17), Adsense has generated $4818.15.
Since I started using Google Analytics in 2008, my site has had 700,000 unique visitors. My sites daily activity between 2008-2013 was between 500-1000 and from 2013 onwards its been 200-350.
I know Army.ca is probably 10x as busy if not more. With Adsense installed, cash would just deposit itself into a bank account. I would estimate the bill would be half way payed for and would not impact user experience.