In reply to henwardian:
Impossible to answer I would say on basis of only the details given, sorry. It could potentially be hugely variable so you will need to give a lot more info.
For example - What’s it current use, current tenure or proposed tenure (short term/long term/restricted use of say grazing let/etc.) current state (used/abandoned, flat/steep, economically improvable or unlikely), any convenants/title restrictions, past use, currently occupied or vacant, size of site, access to site, potential of site for current or past use, utilities on site, registered croft land, deregistered or never been croft, proposed use by tenant, etc., etc.?
In a past job, I’ve let registered croft land for crofting purposes from <£1 /acre upwards. On the other hand non croft for many hundreds/acre in similar land and island location to I of S. I should say I have no current or recent enough knowledge on rent valuations so can’t answer. However, if you could give further info, someone on here maybe able to give a realistic range.