For a noble disciple, my impression is loss (alābho) in AN 8.6 refers to loss of social &/or physical things, such as loss of devotee benefaction thus loss of alms food or shelter, etc, or loss of physical health; or loss of disciples.
AN 8.61 is specifically on the topic of the material gains (lābho) of monks. AN 8.61 says:
First, when a mendicant stays secluded, living independently, a desire
arises for material possessions. They try hard, strive, and make an
effort to get them. But material possessions don’t come to them. And
so they sorrow and wail and lament, beating their breast and falling
into confusion because they don’t get those material possessions. This
is called a mendicant who lives desiring material possessions. They
try hard, strive, and make an effort to get them. But when possessions
don’t come to them, they sorrow and lament. They’ve fallen from the
true teaching.
Next, when a mendicant stays secluded, living independently, a desire arises for material possessions.
They don’t try hard, strive, and make an effort to get them.
But material possessions do come to them.
But they don’t become indulgent and fall into negligence regarding those material possessions.
This is called
a mendicant who lives desiring material possessions. They don’t try hard, strive, and make an effort to get them. And when possessions come to them, they don’t become intoxicated and negligent. They haven’t fallen from the true teaching.
In both AN 8.6 & AN 8.61, the Pali word for (material) 'gain' or 'possession' here is 'lābha'. I guess if the gain was a mental gain, the Pali might be 'paṭilābha', such as in:
Monks, there are four acquisitions (paṭilābhā) of individual character
(attabhāva):
(i) From one's own volition but not the volition of
others;
(ii) From not one's own volition but from the volition of
others;
(iii) From both one's own volition & from the volition of
others;
(iv) Neither from both one's own volition nor from the
volition of others.
AN 4.171
Paṭilābho, used in SN 55.1 about obtaining the four factors of stream-entry; AN 8.2 about obtaining
the wisdom fundamental to the holy life; AN 4.171 about acquiring individual character;vMN 106 about obtaining equanimity; SN 42.8 about acquiring a view; Dhp 333 about acquisition/gaining of wisdom.
We can research more later, however the following sutta also seems to support my theory, where social & physical acquisitions are 'labha' and where the mental acquisition of faith is 'paṭilabha'.
But what of the unsurpassable acquisition?
Lābhānuttariyañca kathaṁ hoti?
Some people acquire a child, a wife, wealth, or a diverse spectrum of things; or they acquire faith in an ascetic or brahmin of wrong view and wrong practice.
Idha, bhikkhave, ekacco puttalābhampi labhati, dāralābhampi labhati, dhanalābhampi labhati, uccāvacaṁ vā pana lābhaṁ labhati, samaṇe vā brāhmaṇe vā micchādiṭṭhike micchāpaṭipanne saddhaṁ paṭilabhati.
There is such an acquisition, I don’t deny it.
Attheso, bhikkhave, lābho; neso natthīti vadāmi.
That acquisition … doesn’t lead to extinguishment.
So ca kho eso, bhikkhave, lābho hīno gammo pothujjaniko anariyo anatthasaṁhito, na nibbidāya na virāgāya na nirodhāya na upasamāya na abhiññāya na sambodhāya na nibbānāya saṁvattati.
The unsurpassable acquisition is when someone with settled faith and
love, sure and devoted, acquires faith in a Realized One or their
disciple. …
Yo ca kho, bhikkhave, tathāgate vā tathāgatasāvake vā saddhaṁ
paṭilabhati niviṭṭhasaddho niviṭṭhapemo ekantagato abhippasanno,
etadānuttariyaṁ, bhikkhave, lābhānaṁ sattānaṁ visuddhiyā
sokaparidevānaṁ samatikkamāya dukkhadomanassānaṁ atthaṅgamāya ñāyassa
adhigamāya nibbānassa sacchikiriyāya, yadidaṁ tathāgate vā
tathāgatasāvake vā saddhaṁ paṭilabhati niviṭṭhasaddho niviṭṭhapemo
ekantagato abhippasanno.
AN 6.30