Explain dispute about damaged rows on Bava Kamma 6b?

Question

I was learning Bava Kamma 6b and am having trouble understanding the machlokes between R' Yismael and R' Akiva.

One problem I'm having is at the part of the sugya with Rav Idi bar Avin, he said that R' Yishmael is talking about a case where the animal ate a "row amongst the rows", there are heavy-fruit rows and weak rows nearby (because if there was only one type we'd probably assume that the eaten row was of that type) and we don't know which type of row was eaten, so because of a doubt, the damager has to pay as if he damaged a full row.

But the Gemara right afterwards says that this is a case of "one extracting money from his friend, and the burden of proof is on him" -- when someone (the damaged party) wants to take away money from the damager, he has to prove that it was the best row eaten, and if not then he's only entitled to the weakest row. What did the previous part assume, to say that he pays for a full row? It doesn't explain what the actual argument is. What would R' Akiva hold if it was a "row between the rows", he would hold the opposite that he pays the value of a weak one? But R' Akiva only obligates him for the actual value, so would he agree with R' Yishmael that he pays for a full one? But then what would the argument be at that point?

And also the previous section in fact did take into account that "one who takes money from his friend has to pay", since it (a.k.a., Rashi) said that the row is amongst big and small rows, the simple reason for Rashi saying that is probably because if it was only among weak ones, for sure the damaged one has to prove himself that it was a big row before demanding it, so what changed in between the 2 sections of the Gemara?

Answer 1

Lets say high quality patch (or row) was worth $50 and the same size lower quality patch is worth $25.

Tosfos Bav Kama 6a explains that according to Rav Idi Bar Avin, the hava Amina (first assumption later proven incorrect) of Gemara assumed that Rabbi Akiva says we only pay the minimum amount when unsure how much it was worth only Rabbi Yishmael says pay maximum:

אמר רבי עקיבא לא בא הכתוב אלא לגבות לניזקין מן העידית משמע ששמע מר' ישמעאל שבא הכתוב לחייב יותר ממה שהזיק כגון דאם אכל כחושה משלם שמינה:
Rabbi Akiva says the Passuk is only requiring the damager paying highest quality land he has i.e but no more than the minimum, since he heard Rabbi Yishmael saying he would pay when in doubt the maximum (e.g When unsure of damage if the Minimum damage was $25 and maximum was $50 Rabbi Akiva says pay $25 from vandal's best land, Rabbi Yishmael pay $50 which is the victims best patch)

However in the Maskana (conclusion) of the Gemora Rav Acha bar Yaakov explains both Rabbi Yishmael and Rabbi Akiva agree Hamotzi mechaveiro alav haraaya One pays the minimum amount without any further proof, so the payment both according to Rabbi Akiva and Rabbi Yishmael is only $25 . Their dispute is which type of land to pay when they are rich:

כגון שהיתה עידית דניזק כזיבורית דמזיק ובהא פליגי רבי ישמעאל סבר בדניזק שיימינן ורבי עקיבא סבר בדמזיק שיימינן
- If a rich man damages a a poor man's best land (e.g which is a $25 patch),Rabbi Yishmael says one who is rich and his low quality land is worth the same as the poor mans best ($25 a patch) pays that low quality land.(The rich man has even better produce worth $50 a row which he keeps).
- Rabbi Akiva argues that this rich man should pay his own best quality land - so if an equivalent size patch is worth double ($50) he pays half a patch (worth $25) which is worth the same as a full patch of land of the poor man which he damaged*

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*Note:
1. if a poor man damaged a rich man, Rabbi Akiva and Rabbi Yishmael agree he can only give the value of damage with the best land he's got (e.g if he damaged $50 patch he pays 2 patches of his best $25 patches)(Tosfos Kegon Gittin 49a).
2. if a rich mans damages a poor mans land (worth $25) and his worst land was better than the poor mans best land, (e.g poor mans best is $25, Rich mans worst $50 rich mans best is $100 a patch) Rabbi Yishmael agrees to Rabbi Akiva the rich man pays the damage equivalent with his own best (i.e a quater of the $100 patch) in accordance with the Torah (Bava Kama 6b).
3. Also If one wants to he can pay money/movable goods instead of land as Bava Kama 7a says ישיב לרבות שוה כסף.
(Summary of Bava Kama 6a and Gittin 48b-49a:)