the troops that come in are random. The price of them however is suppose to be a bonus.
troops only cost silver... so if your well stocked your good.
the reason they cost high is because there is no training time involved. The troops are ready as soon as you have the coin. Kind of like mercenaries
Because you can get troops that you dont even have to research... and no training time... and no favor cost in the form of myth units.. of course it costs more. Merchants have to feed their kids.