This emotive subject has been discussed before on here.
Keep things in perspective.
Firstly, what are the 3 species? I don't know the area or what is there but if it were red, fallow and Sika giving big body weights and the venison is yours to sell, then £1250 per rifle for 4 on a syndicate shooting say 2 or 3 mature stags/bucks, a couple of young ones plus the remainder in hinds/does works out at 4 beasts per rifle.
If you want to go on the hill for a stag for one day stalking it will be about £400 even if none are shot. No venison to keep or sell to offset costs either.
If a group of close friends took that on and split the beasts shot fairly over 4 years giving every member a share of mature males it is not actually that bad a deal when compared to guided stalking IMO.
Plus there is nothing to stop a couple of members going out together experiencing their mates success should they have shot their quota for that season first.
In this day and age where stalking is not exactly plentiful and folk are paying for more and more outings,then this whilst not a bargain is a reasonable opportunity.
Depending on species and type of ground obviously.
The add suggests however that the surrounding areas are where the beasts are appearing from which if the case would be a worry. The 650acres would have to hold its own stock to be worth it...