I wouldn't stress about getting 80x50cm cages for everyone, I know people who swear by cages as small as 60x40cm (or smaller) for pairs right through to some who swear by 80x50cm or even 100x50cm for pairs. I now start pairs in something fairly small (like a mini duna) and go from there unless I know they were kept in bigger before I got them, if they were kept in bigger before then I'll try to match that and if they seem like they'd be happy with larger than a mini duna I'll consider trying them in 70x40cm or similar after a few weeks. When I joined this forum 70x40cm seemed to be about the usual suggested cage size for a pair and starting with that or smaller has always gone well for me.
I've kept some groups over the years and I found 80x50cm worked really well for a group of four I had. They were also okay in 100x50cm but any larger and they stopped getting along very well at all. There's not really an exact science to it and a lot of people will have different opinions, but I'd try to not worry too much about other opinions and go for whatever works for you and your hamsters. I don't go in for having one of everything per hamster either, I try to give one wheel each and its good to have multiple houses (with more than one entrance/exit) but I'd be quite happy giving a pair one toilet roll tube or one log bridge to share.
Even if the worst happens and everyone ends up alone, you may find that you don't need huge cages for them all, even for single hamsters cage sizes are a subject where everyone has a different opinion but I've got a few robos in cages about 55x40cm and all three are totally happy in them. Best of luck with your robos, I hope you can find something that works for you and for them and that they do well in pairs/groups for you
