There are, then, many ways to make your money go farther on a trip to Shetland. There are so many permutations that it’s impossible to answer that question definitively, but here’s a worked example.
We’ve excluded food, partly because – if you’re mainly self-catering – the cost is unlikely to be very different from what you’d spend at home, and partly because some budgets will be more flexible than others. Nevertheless, you can eat very well in cafés, restaurants and from takeaways, so maybe you can allow for the occasional indulgence.
Let’s assume for the moment that you’ve made it to Aberdeen and plan a seven-night trip including two nights on the ferry. The first set of calculations below assumes that you’d like a reasonably comfortable voyage but without the expense of a cabin.
If you were to use a lie-flat sleeping pod both ways on the ferry from Aberdeen (£152 return in peak season), stay five nights, paying on average £40 per person per night for accommodation (£200) and spend, on average, around £5 a day on bus or ferry fares (£25), you could enjoy a week in Shetland for around £380, plus whatever cost is involved in getting to Aberdeen. Travelling in mid season would cut that by £15, and if you were to travel in low season, you’d save another £16, or £31 in total. As explained above, travelling between islands won’t add much to your costs, with the exception of flights to Fair Isle or Foula.
How low can you go? Well, if you brought your own tent and a bike (which is free on the ferry), travelled without accommodation on the boat, and wild-camped, your outlay (from Aberdeen) in peak season would be £92, dropping to £76 in mid season and £59 in low season. Even if you added a reclining seat each way, costing £7 return, the peak season cost would still be just under £100. Of course, you’d probably want to spend some money on occasional treats, such as a meal in a café or restaurant, or a takeaway, or perhaps on, say, a ticket to Jarlshof, so £150 - £200 would be more realistic, and to keep costs down, you'd need to use the least expensive route to Aberdeen.
These costs can only be an indication, as it will all depend on which travel and accommodation options you choose and how much money you spend on entrance fees, on eating out or on internal travel, for example to the northern islands of Yell, Unst and Fetlar.
On that theme, it’s worth mentioning that many of Shetland’s best experiences are free to visit, including such historical sites as Clickimin Broch and Muness Castle. The excellent Shetland Museum is also free, though a donation is appreciated.