Hi Orion:
That's an old scare tactic. "The other guy sells crud. I have the only good product!" Ignore it.

I have a 16'x40' and it's a custom size. Still, a replacement liner is about $1000--for the liner. Add that to the water for $700, and you've got about $700 for the labor. Seems $2400 for the job is fair to me.

But get references. Not EVERY vender here is a scam artist, but you must hunt.