Dear Artist, We always try to do our best. Presumably we only put our best into galleries. Work below a certain standard is rejected by the prudent artist and relegated either to the bonfire or to long-term storage. In the remaining better work the artist is often able to determine a further range in quality. Now let's look at another situation.
Galleries work on varying commissions.
Also in my case there seems to be no rhyme nor reason why one gallery ought to be granted more than the other. Then some other galleries improved their capabilities but continued along at the lower rate. Sometimes the expensive galleries dwindled off or changed direction and taste. You'd better not mention this to anyone if you decide to try it. And the bank.