Presumably, this answer is correct - the Beraisa
continues, 'R. Yehudah admits, if he was sent to buy
legumes (and spent half the money on legumes, half
on something else) Reuven also transgresses Me'ilah
- legumes are sold at the same rate whether one buys
a lot or a little.'
I UNDERSTAND: LEGUMES THAT THEIR PRICE WOULD REDUCE IN LARGE QUANTITY - R.
YEHUDA WILL SAY THAT REHUVEN (BA'AL HAMAOT)
COULD SAY: i wanted large amount and you gave me less that i nedded -
or maybe it's different - since the SHALIACH will say: you have nothing to
do with large amount (not like the cloak which undoubtally he needs one!)
Rav Yehudah admits that a half of Shelichus is also a Shelichus as long as the Ba'al ha'Bayis does not lose anything. Therefore, if the price would have gone down by buying a large amount, the Ba'al ha'Bayis is not Mo'el even on the half, for he paid a higher price. However, if there is no difference in price, then he got what he wanted in the first half .