You are absolutely right and that jumped out at me. I should also point out the obvious: if people were selling online assets making $9k/year for $9k, there would be a line out the door of people lining up to buy them. If anyone here is selling an asset that makes $X a year for $X, I'll buy it! I make my money back in 12 months and everything else is profit.

So let's value it as it would be valued on, say, Flippa, a decent proxy for "the market." We would look at the monthly revenue: in this case, around $750/mo (which is 9k divided by 12). Then we'd do a multiple of the monthly revenue: 20 is low, 40 is normal. I would actually say 30 here, because this guy created the asset and I would bet he did it well and it's not junk. So let's say it's worth $22.5k.

So I think it would be more accurate to say, "I purchased the site in a deal through assets valued at about $42k, total."

[edit: updated the comment as I got confused about the thing being exchanged - it's a site the guy created that he transferred to make the sale]