Сдерживать падение цен

[e-sve]

Контекст

Однако, несмотря на серьезное падение спроса и общую тенденцию к снижению цен, риэлторы старались сдерживать падение цен.

Мое начало

However, despite a tremendous decrease of the demand and a tendency for price abatement, realtors did their best to prevent ....

спасибо

[Irisha]

to avoid downward spiraling of prices
хотя для "общую тенденцию к снижению цен" тоже downward можно использовать - overall downward trend

decline/collapse...

[kinsman]

Имхо:
However, in the face of/challenged by/facing/having/left to deal with plummeting demand and a general downward price trend real estate agents went to a lot of trouble, made an all-out efforts, took great pains to prevent a drop in prices

[Ken Golovin]

despite a considerable drop in demand and a general downward trend in the market, realtors held on to keep the prices up

IMO

[e-sve]

Всем спасибо!

[V]

also, consider

To control / curb

(downward spiral, drop etc)