tbh, the 30x30x30cm ext terra is ideal for 2 - 3, i dont think a wooden viv is too good as they need humidity, but im unsure, if it is ok then the cost about £20 each and you could easily house 10-15 in there
Although they need a high humidity, a good air flow from good ventilation is also essential, couldn't spot any ventilation in the picture. Also, using a wooden viv for a high humidity environment means you risk the wood swelling.
We paid £100 for 1.2 pygmy chams, they were £45 each. Weve seen cheaper online but by the time youve paid £30 postage works out more or less the same. Ours are in a 30x30x45 exo terra and its perfect really. I wouldnt think a wooden viv would suit them much they also preffer the height to climb, anything too big and they will kind of get lost in it and have trouble finding food etc.