first off, the devs have probably already been paid, by the publisher. they get a lump sum to develop the title, and then some small royalty amount for additional sales beyond a certain level. a game has to really break the bank open for the royalties to be worth more than chump change.
second of all, the publisher gets paid by the retail chains and the warehouses for specific shipments. even if atlus loli rpg #199 only sold through 158 copies to the internet pedo community, atlus already made its money when it sold the initial 10,000 copy production run to the retailers/warehouses. until another shipment is requested by the retailers/wholesalers from the publisher, no additional royalties will be paid, either.
the ONLY scenario where the dev gets extra dollars based on marginal additional sales is when the dev house themselves publishes, distributes, and sells the game themselves over the internet or through mail-order, OR when a game has a very conservative sales estimate and then has demand rocket whereby the publisher gets additional orders above and beyond the set order schedule.
really, at the end of the day, a games sales are determined in the first three weeks. buying used for 90% of the games that don't have an unanticipated long shelf life won't hurt the devs at all, and it clearly benefits the asshole retailers. publishers are the ones that get stuck buying back unsold copies in many cases, so while buying used does a little bad in overall sales margins and long-term sales schedules, it also does a little good by dicking over publishers. it's largely a neutral exercise overall.
