we are looking at becoming an anchor for assets like BTC and ETH, but I don't understand what the business model would be for that. Do any of the current anchors for these assets charge any fees? For example, i looked at apay.io and there is no mention of fees or business model. How do companies that sponsor assets make money in general?
Many(most?) anchors have withdrawal fees, including apay.io (https://apay.io/out).
Another possibility is working with other businesses and charging them a fee to use it - but this is probably more common with fiat anchors.