Depending on ribbon length , each 90m cart does about .74 sq meters , for a cmyk job you use 4 carts pers sq meter.
There is some saving in terms of yield by using the ribbon saver. If you take your labels , at 200 x 150mm , the area printed is 0.03m squared and 100 of them is 3 m squared which does equate to 4 carts , considering you used cmyk to get red , you have used 8 carts (as mike said , set it to use a single colour , you get spot red carts)
Essentially without vinyl , the cost of those stickers was pretty high , even at 4 carts or using refil ribbons , the cost per decal to print is not great.
a 90m spot refill ribbon costs us around 10 quid , thus the labels cost at best , 40 pence each to print , add in the vinyl and you are probably looking at 60+ pence and a selling price of at LEAST 2-3x that.
In your case , the lables will have cost almost a quid each.
The better thing to do on these machines is very small die cut shaped stuff and metallic spots on dark , once you get into the type of thing you did , you compete with other technologies. For example on my inkjet , even at a real high price , those decals would sell at 1.25 -1.50 and would cost me 18-22p and thats using a 10 yr premium vinyl.
If the lines do not dissapear with the pitch adjustment and are white , I am afraid that they might be a blown head.