This topic is raised every now and then and I thought it was time that it was revisited as I noticed this ad on eBay UK but there are plenty of these shonks in the USA and everywhere else.
Domestic sewing machines are not for leather! Yes they can sew a couple of layers of upholstery leather or even do what this advertiser has done but all you are getting is a $25 machine for $400. It won't feed properly, cannot handle anything more than #69 thread and it is going to crap itself very quickly
The term "semi industrial" is meaningless and I always ask people what "semi industry" they would use it in.
The advertised machine is a Singer 99k which absolutely the worst possible Singer vintage domestic straight sewer for leather.
http://www.ebay.co.uk/itm/Semi-Industrial-Singer-99k-Mk2-Sewing-Machine-Heavy-Duty-Leather-New-Motor/292011554953?_trksid=p2047675.c100011.m1850&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D1%26asc%3D43782%26meid%3Dcb77f3de8b45407589eedd77e6a51505%26pid%3D100011%26rk%3D1%26rkt%3D12%26mehot%3Dpp%26sd%3D252912248287