Would you please explain to me what does the speaker mean
by (even a town next to it would have much cheaper housing)
what he means by this phrase
Well, Brentwood is particularly expensive just because it's a desirable place to live and it's proximity to London also makes it, the housing is quite expensive, even a town next to it would have much cheaper housing
The houses in Brentwood are way more expensive than even the expensive houses in the town(s) next to it The reason the houses are so expensive in Brentwood has to do with the fact that its closer to London (it's convenient for commuters) and the fact that it's a desirable place to live (affluent people live there). If affluent people didn't live there and if it weren't closer to London, then the houses would probably be around the same price as the houses in the surrounding towns.