From that entry:
From: someone
In other words, intentional removal of another's chattel under the mistaken belief that it belongs to the actor does not relieve actor of liability under conversion.
From: someone
It does not matter if the defendant made a mistake.
It says nothing about the plaintiff making a mistake, and nothing about property that has been bought.
All it seems to suggest is that the defendent must have intent to interfere with the property of another without legal justification.
If the act of buying something at a price you set and advertise is conversion, then every product you ever bought is subject to price hikes whenever a manufacturer feels they may not have got as much of your money as they would like.
If I sold you a plot at 10K last week, I might decide it's actually worth 20K this week, especially if you flip the land and set it at that price. Does that mean I can sue you?
The example they give for intangible property is that of a certain domain name. That case was conversion because the defendent set out to take away the domain name with no legal right to do so. There was no sale involved.
There is also no mention of which countries laws the text is based on.
In the UK at least, a seller has a right to refuse a sale. Honoring the sale would constitute the entering of a contract to sell at that price. Just look at argos, who were legally forced to sell lots of TV sets at something like £5($10) a piece after a pricing glitch on their website.
The fact that an automated system is used to sell the land with no option to deny the sale wouldn't make any difference over here. Whether that holds true in California or Texas, I don't know, but it doesn't look like conversion as explained in the wikipedia entry.