Suggestion (R. Tam): "Ilisa" is not literally an attic [full of coins]. It is an exaggeration, like "13 camels of Safek Tereifos" (Chulin 95b), like Rashi explained there.

Rejection (R. Tam): Since it says "he entered one, and his son entered six", this shows that it is not an exaggeration. Rather, it is precise!

Explanation (R. Tam): "Ilisa" is a Kli used to draw wine and oil, like we say in Eruvin (53b) "Alas (the pitcher used to draw wine from the barrel) bangs on [the bottom of] the barrel (it is empty)."

Question: We say in Kidushin (29a) that if one did Meshichah on Hekdesh [in order to redeem it] when it was worth 200, and before he redeemed it the price dropped to 100, he gives 200 [to redeem it], for people should not have greater rights than Hekdesh. [If one did Meshichah to buy] from a person, he acquires once he did Meshichah [and pays its value at that time].

Now (based on our Gemara), even if he did not do Meshichah, since he said that he will redeem it for 200 [he must pay 200], since saying [that he will give] to Hekdesh is like Mesirah to a person!

Answer: There, he is not obligated to pay 200 based on his speech, because he did not say to give anything to Hekdesh. It is not a vow, for he said only that he will buy for the value;

However, if he pardoned anything of his to Hekdesh, he must fulfill it, since saying to Hekdesh...

Explanation (Rashba): The man who wrote his property to Yehonason ben Uziel vowed that his sons not benefit from his property in his life and after his death. Shamai thought that he gave to Yehonason on condition that he will give to [the giver's] sons;

[Shamai] thought that [Yehonason] returned everything [to the sons]. Therefore, he came to say that through this gift, the sons were not permitted, like the case of Beis Choron, in which the father was not permitted through the son's gift;

Yehonason answered him "it is not like you think. There, it was not a full gift. However, this was a full gift to sell and make Hekdesh.

Support: The Yerushalmi in Nedarim connotes like this. It says that Yehonason ben Uziel's father vowed that [Yehonason] not benefit from his property, and he wrote his property to Shamai;

What did Shamai do? He sold part, was Makdish part, and gave to [Yehonason] the rest. He said [whoever will contest this gift, he will take from the buyer and from Hekdesh, and afterwards he will take from [Yehonason].

Perhaps it was this episode itself, and the Yerushalmi switches it.