Back in the early-mid 90s I was buying hair systems by Rene Duval that used a product they called 'Hollywood Lace' That was much finer than monofilament and allowed you to expose the hairline.
I was buying the at wholesale prices for about as much as I would now pay for an average priced piece sold at retail.

The same company is still selling the same product today, though they've changed the name to Celebrity Lace, presumably to avoid confusion with the retailer called 'Hollywood Lace'.