Some sellers will accept offers for items they've listed on the Loupe Market. If this is the case, you will see the "Offers" button listed on their market listing. If that button is not present, the seller is firm on their listing price, and is not accepting offers on that item.
This means the seller has set an offer amount for their listing, and would be willing to accept an offer around that amount! To submit an offer, simply tap that button
Once you've opened the offer screen, you will be presented with the ability to submit an offer to the user.
The minimum offer amount is $5. Offers are automatically processed, and if the submitted offer is too low, the offer will be automatically declined.
If the offer is within the seller's accepted range, it will be automatically accepted, and you will be prompted to complete your purchase at that time via Apple Pay or Google Pay (dependent on your device).