One inch of XPS has an R Value of 4.5-5, which should be sufficient to prevent condensation on the rim. However, it is way below the recommended insulation values for your climate. The US Department of Energy recommends R30 for walls. The rim area, which is abovegrade is, in effect, a wall. So any suitable insulation up to that R value will be effective. At the least, I would add batts. You could also use EPS (expanded polystyrene) in addition to or instead of the XPS. It has a lower R Value per inch than XPS, so you'll need more. But it's cheaper. Polyisocyanurate boards with a foil covering will give you up to R8 per inch and are usually not required to be covered by any other fire resistant materials. ****** I find it virtually impossible to use the handheld foam can upside down in the cramped spaces between the joists. So I cut the foam tight and use caulking. But maybe that's just me!

I used 2" and cut the pieces out of a 4x8 sheet and cut them 1/4" or so shy of the average bay sizes to give room for the foam to go in. I had a few that didn't want to stay against the rim joist as they were foamed and I didn't have any washer nails to hold them in tight. The few that gave me trouble got marked with a marker and I drilled a few holes in the foam board and shot foam in the back side and let it sneak back out the holes and shaved the excess off. it is a night and day difference between the foam board and just having batting stuffed up in the spots. I don't have a heated basement and can tell a world of difference. I think I got around 30 plugs out of one 2" 4x8 sheet of foam board with a few pieces left over for odd sized spots. One can of great stuff foam did between 8-10 plugs with a price around 6 bucks a can and the sheet price of $22.50. Once you get set up and going it doesn't take too awful long to do. I got the ones with obstructions fitted with a hand saw and in place first and then stuck 10-12 in a row so I just had to concentrate on foaming. I noticed that if you spend too much time putting the foam blocks in after the can has been partially used it wouldn't go near as far as if you started foaming and went from one to the next.

Stopping air leaks from the exterior is only part of the story. You also need to stop warm interior air from hitting the rim from the inside and condensing there into ice and feeding mould growth on the fibrous insulation in the rim. Do those bags create an air barrier to inside air? How are they affected by moisture? If you wouldn't blow in netted cellulose to rims, is there a difference if you put it in a bag? Not for me. Afraid I'm a fan of spray foam, even when you are required to cover it with a thermal or ignition barrier.

If they are using foam cans it isnt going to look as nice as what you see on tv with the spray guns. In any case, make sure they seal between the sill plate and the concrete also and not just the rim joist. The sill plate can allow large drafts if not sealed. With your reasonable cost they gave you, they are probably using cans, if you wanted them to get a spray foam contractor with a gun or get a spray gun kit the cost would be more. Are you going to be seeing this daily or are you finishing the basement? If you wont be seeing it, this should be a non-issue.