Aussiemaddog, the takeover premium doesn't really have any correlation with the stock's intrinsic value.
The acquirer will usually do a detailed analysis similar to what you have done. Just say they come up with the same 1.28 value, then they will compare this to the current SP of 62c and say "even if we offer shareholders a 30% or so premium to the current SP to convince them to sell to us, which will be around 80c to 85c, then this is still a good deal".
I also note the $25m cash balance was as at the end of Feb, so we should have another 1.5 months of cash now which is around another 8m or so.
EXS Price at posting:
62.0¢ Sentiment: LT Buy Disclosure: Held