I have a 111w155 walking foot Singer and love it! If the one you are looking at is 111w152 it is made for lighter weight fabric but still will do heavier work then we should be making our household machines do. I use mine for lots of things but mostly dog toys and now that I have the servo motor with the needle down positioner I am in total love with it. I have fixed the neightbors paintball vest, sewn awnings for my husbands camper and vinyl for covering chairs for our nephew. Lots of things and I liked it before but now like I said with the Servo motor feels a lot safer as these machines can take off on you. My cousin had to make a special adapter for the needle positioner and that really helps me with controling everything so much better. They are great machines even though there is no reverse. I can't speak highly enough about the industrial or commercial machines. They let me do so much more and I don't worry about breaking the household machines any more! We actually got another 111w155 in Michigan for $75. that went to my cousins son and he does leather with it and is very happy also.
Here is the manual that covers the 152 model also:
http://parts.singerco.com/IPinstManu..._W154_W155.pdf
Hope this helps but I think $450 is on the high end but not excessive. I have spent that much on a commercial 4 thread serger and am very happy to have it. We have just been very lucky and happened upon the cheaper ones. Definitely worth it once you have everything going. There is a lot more mechanically involved with this machine because of the walking foot but if this one is working well you will only have cleaning and maybe a Servo motor down the road.
Again I can't say enough about these machines and am very glad I have them. Don't use it all the time but when I want to make anything heavy heavy duty I know I can and don't have to worry.
Good Luck!
Lisa