I just use 1757 shares of IBIT = 1 BTC. This fluctuates constantly, but not by a whole lot.
Historically there is a +/- 1.5% fluctuation from that 1757 base.

NAV here means number of bitcoins held divided by number of shares

$105k / 1757 = ~$59.76 per share
$500k / 1757 = ~$284.64 per share
$1mil / 1757 = ~$569.29 per share

Actual custody is for retards.