yup, i recently did some modelling on my HSA account to solve a similar problem
It has a savings portion at like .05% and has $5.50 a month in service fees until $5000 balance (3.50 for account maintenance, and $2 for brokerage link). An hsa only lets you put in 3400 a year per IRS requirements.
my model was, now that i'm on year 2, i have covered the 5k in the account. Does it make more sense to keep paying the 5.50 fee per month, or put the 5k in the cash portion to stop paying the fees and re-start the investing going forward.
I ran a few models with some spread in between.
all cash to 0 vest
5% cash to 95% vest
all the way down to
0 cash 100% vest, factoring out the fee each time.
Assuming more than a few percent in returns, it makes the most sense to continue paying the fee as I earn an average of $4 in a day and the other 29 days of the month are profit vs if it was in cash. As the balances go up, that day time period turns into hours and then minuets.
The bank makes out - I make out. it sucks that it's the best way and they know it and profit off of it.