Raid of 9 or more disks on a hardware controller?

Question

RAID

Greetings! Who had the experience of assembling / exploiting the subject, please share.
There is an adaptec 6405 - it has the ability to be connected to 4 sas / sata disks using a special wire, and also, following from the description, to 256 devices using a sas expander. Do I understand correctly that in order to connect more than 4 devices, it will be necessary to connect these same sas expander in series (the first one found in the search engine AEC-82885T)?

Например, [adaptec6405]=======[AEC-82885T № 1 ]========[AEC-82885T № N ]==============[AEC-82885T № 32]
                        [hdd 1] [hdd 2] [hdd 3] [hdd 4]                      [hdd 249] [hdd 250] [hdd 251] [hdd 252]
                        [hdd 5] [hdd 6] [hdd 7] [hdd 8]                      [hdd 253] [hdd 254] [hdd 255] [hdd 256]

Well, this is of course rough, for clarity. This is the first thing that came to mind, so I'm almost sure that the scheme will be different. Kick in the right direction please.
Also confuses the cost of the expander - it is more expensive than the controller itself - is this normal?
And yet, the expander itself will naturally not work without a controller?