A topic where you ask people to guess the price and give their reasoning would not be incentivized posting warranting movement to Games & Rounds. But because there is a prize, it is incentivized posting and should be moved to Games & Rounds according to the rules-as-written.

However: Almost all rules are subject to mod discretion. The reason for the rule against games with incentivized posting outside of "Games & Rounds" is to prevent unfair/excessive bumping and "last-posts"-filling except in "quarantine" sections which people can ignore.  In El duderino_'s games:
 - El duderino has no incentive to cause spammy replies. The prize is a true gift.
 - The game has a pretty high entry requirement which prevents the replies from actually becoming spammy.
 - El duderino_ very much prefers that the games be in Speculation rather than Games & Rounds.

Therefore, it's most appropriate in this case to apply mod discretion and make an exception to the rules as written; El duderino_'s future games of this sort can stay in Speculation.