Was Kraznys a bit dumb thinking that his deal to sell all the unsullied to Dany for a dragon was a good one? What’s he even going to do with a dragon, realistically? This plot device always seemed a tad contrived but would be interested to hear your thoughts.
To be sure, the author very clearly portrays Kraznys as foolishly arrogant, almost comically exaggeratedly so (except for the evil he represented and embodied). Kraznys cannot refer to Dany except via sneering and misogynistic insults - the “Westerosi whore”, the “sunset savage” - while simultaneously lusting after her. Kraznys’ contemptuous assumption that Dany could not possibly understand High Valyrian provides satisfying dramatic irony for the reader, as Dany mentally translates each of Kraznys’ slurs and barbs while pretending not to understand them, all the while formulating a plan of her own. So right away, long before the pretended handover of Drogon, the reader can reasonably expect that there will be some sort of comeuppance for Kraznys and the rest of the Good Masters, some way in which these evil men will ultimately fail through their hubris.
It is also worth pointing out that it is Dany’s idea, rather than Kraznys’ or any of the other Good Masters, to (pretend to) sell Drogon to the Good Masters. However much the Good Masters may have wanted one of Dany’s dragons - more on that in a minute - I do not think any of them was necessarily going to suggest that one or more of the dragons was or were (or could be) on the bargaining table without Dany first saying so. Indeed, Kraznys urges his compatriots to charge triple or even ten times the price of each enslaved person, without quantifying what such a price might mean to Dany, while the other Good Masters suggest that Dany sell her crown or give a show of reluctant acceptance to her offer of her cogs. So I think it’s fair to say that neither Kraznys nor the Good Masters necessarily anticipated that Dany would offer one of her dragons, even if they were not at all displeased that she does so.
Now, I think Dany cleverly seizes on why Kraznys and the Good Masters of Astapor would leap at the chance to “buy” a dragon. First, on a more general level, Dany was by this point well aware that her dragons were spectacular, a wonder that had not been seen for well over a century (and presumably much longer in Essos). After all, I do not think it is coincidental that for the negotiation with the Good Masters, Dany chooses a Qartheen gown: her clothing acts as a subtle reminder of her recent celebrity status as the Mother of Dragons. What Dany is offering by putting Drogon (ostensibly) on the table is almost literally priceless - think of her half-teasing remark to Xaro back in Qarth, that the value of one of three living dragons in the world should be at least one-third of all the ships in the world - and so will absolutely end the conversation when it comes to Dany’s plan to “buy”, then immediately manumit and liberate, the enslaved people of Astapor.
As for the second point, Dany herself thinks it immediately after the offer is made:
She knew the answer, though; she could see it in the glitter of their eyes and the smiles they tried so hard to hide. Astapor had thousands of eunuchs, and even more slave boys waiting to be cut, but there were only three living dragons in all the great wide world. And the Ghiscari lust for dragons. How could they not? Five times had Old Ghis contended with Valyria when the world was young, and five times gone down to bleak defeat. For the Freehold had dragons, and the Empire had none.
In the crumbling ruin of Astapor, the Good Masters cling in vain to the prestige of the long-dead Old Empire of Ghis. Their entire existence rests on the legacy of an empire which had met its “bleak defeat” at not just the hands but specifically the wings, claws, and flames of the Valyrian dragons. Now, however, the Good Masters have the last descendant of those Valyrian dragonlords, the only person with dragons in the whole world, seemingly willing to give away the largest and strongest of her miracles for enslaved people - people whom, the Good Masters surely anticipated, they could and would replace quite easily in the future in the unceasing churn of human misery that was the Essosi slave trade. This surely seemed like the ultimate achievement for the Astapori: they whose ancestors had been so roundly defeated by the dragonriding Valyrians, whose greatest city had been not just destroyed but deliberately uninhabitable, could now make this Valyrian descendant their supplicant, and have at their disposal the very sort of creature which had wreaked death and destruction on the Ghiscari long ago. (Compare, for example, the tapestry Barristan Selmy will much later see in King Hizdahr’s apartments in Meereen - showing “the glory of the Old Empire”, including “last survivors of a defeated Valyrian army passing beneath the yoke and being chained” - another grasp by an ambitious Ghiscari descendant seemingly victorious over the Valyrian-blooded Dany.) A dragon was not just the opportunity for martial domination such as the Freehold once claimed, and which now seemed possible to Astapor in turn, but a priceless symbolic triumph: the Good Masters simply could not pass up the opportunity to take a dragon from the representative of Valyria standing before them, and claim the superiority which Valyria had seized from Ghis centuries prior.
