Not speaking about Rodney specifically, but that is a known and accepted technique for limited editions, rather than a gimmick (unless one considers anything and everything related to marketing and sales as a gimmick, of course).
Say you limit it to 50. You can leave it at that, or you can split it into tiers. You can say that after the first 10 are sold, the price for the remaining ones goes up by, say, 20%, and so on for the next tier. The purpose is to entice "early adopters" to buy, hoping it will go up in price. It also rewards the artist if his work becomes more popular. When artists are new and unknown, they tend to price their work low, in desperate need for cash. If they turn out to be good and in demand, they can only watch how someone else on the secondary market is profiting from the popularity of their early works, but not them. When selling in tiers, at least they participate in their works' success.
