as a collector, an acetate is only worth anything to me if it's unreleased or different from the original in some way. Or for certain "holy grail" items it could have value as an oddity or a frameable or collectible object. But an acetate generally isn't functional in the same as a record, you can't just keep playing it over and over. I guess some collectors like an acetate of a released record better because it's "rarer" and one-off but I would rather have the actual record.
also, what makes record collecting different for me than say, art collecting, is that I'm collecting mass produced objects -- even if they are extremely rare and you know someone who has one, it's usually possible for you to find the record you need. You can be a completist and run labels, artists, etc. With art you can't collect every picasso even if you had all the money in the world, as each one is unique and one-off. To me acetates, as one-offs, sort of go against the philosophy of the things I collect which sort of makes them less interesting to me. The ones with the most value to me are the ones that I have via some personal connection with the artist.