Aluminum only looks like it is not very abrasion resistant when you put it next to steel.  Compared to most other boat building materials it is still very abrasion resistant.  The reason I say this is that I was in the position of looking for a boat on the West Coast of Canada a year ago.  I started looking at steel and ended up buying aluminum after looking carefully at the differences.  The two materials are pretty different, but both offer a tolerance to collision that is difficult to achieve in other materials.  So, if you find the right boat, I don't think aluminum or steel should be the deal breaker.  I didn't find a Junk rigged boat, but I did find one with freestanding aluminum masts and most of the other traits I wanted.

As a disclaimer, I should also say I am currently in the process of removing 6000lb of concrete and steel punching ballast and replating the ballast box of the boat.  So when you budget for converting to junk rig, also consider that if you are buying a used boat there are going to be significant restoration costs, some of which you might not anticipate initially.

Cost of the rig, is going to depend a lot on your choices in materials.   Wood, vs aluminum vs carbon fiber masts.  Mustang fabric etc.  Not, to mention all the little bits and consumables.  Mustang fabric alone for sails that size would be roughly $500 per sail (550 sq ft sails and 15% wastage) from a place like Rochford Supply (don't forget to add >$100 for shipping and >$100 for border fees).  The masts will likely depend a lot on what you can get near the boat.  I assume you are not doing the work in Red Deer.  Aluminum flag poles could be a good option depending on where you are, but shipping can become a big part of the equation depending on your location.  Aluminum battens are another case where what you can find locally is going to be more attractive in terms of cost because shipping costs can be a bear.

Sorry I can't provide more detailed numbers, but I was visited by David Tyler and now have the wingsail bug.  My budgeting has been built around that.

Darren

I would imagine there's not a lot of 40' steel boats in Alberta at all. There's a 30' steel junk available in from West Yachts (Anacortes, WA, USA) called 'Furthur', and you'll probably get farther faster like that, you could be cruising next week, and definitely in the spring. There's also an aluminum 40' colvin gazelle from the same broker, but I suspect you're looking for rock poundability from your steel hull. There's also a 50' junk up here at french creek for sale, don't have any info on the hull however.

Are you converting the rig yourself or having the work done? Your costs include masts, sails, battens, yard, rigging. Without a sailplan it's harder to figure out, but let's imagine your steel boat displaces 17 tons. 1200 sqft of sail will give you SA/D of almost 17, fine for cruising. If you put that on 2 masts you'll have 600sqft (55sqm) per mast.  In wood you would go something like (rough estimate) 30cm tapering diameter on a 10m mast, you could spec it out for aluminum or even steel on a boat that size. 

Fabric cost is about $1/sq ft, maybe double that for notions, but the real price is in the labour. I was quoted 2000EUR for a professionally made 30sqm sail a few years ago, I made it myself for probably less than $500 but it took a lot longer. Same with the mast and battens.

Battens and yard depend again on your sailplan. Rope is cheap but blocks can be very expensive. I know some people that have made their own.

You need more work on your specs to price it well. If I had to take a stab at it? $30,000=$10,000 for the masts, another $10,000 for the sails, another $10,000 for battens, rigging, and mast partner modifications. Someone with more experience on larger rigs and more specs on your boat would fine tune that a lot, I'm sure.

Have you read PJR and Arne's book on Cambered Panel Junk Rigs? That will help you a lot with your calculations. I think I still have Arne fever, after finishing my own rigging project I still keep thinking about starting another.

I don't know if there's a rule of thumb based on the boat displacement. That would be nice, but it depends a lot on your sailplan, how you build and your materials.