If you're in a hurry ... you'll have to cough up a hundred bucks an hour or so for the truck ... multiple trips ... as you've discovered.

If you're not in a hurry, fill from the well 15 minutes an hour or so. If you start to suck air .. switch back to plan A above.

We can fill our 16x32 from the well in two days like this.
Beats watching grass grow because every few inches you see it go up, you can think that you just save a hundred bucks.