I'm a late comer to this thread, but here is my take on things. As most people on this board know, prerequisites for shinsa are a polished sword and shirasaya. For a standard length daito, if one were to purchase a "project" bare blade, one is looking at $3000 for a polish+shirasaya, and an extra $400-$500 if one needs a new habaki. In comparison, the cost of the "project" blade is more or less inconsequential. So anytime one contemplates submitting a project blade to shinsa, don't get bogged down in the actual cost paid for the blade. Rather, think of the $3000-$3500. Even of one were lucky enough to get Hozon, the monetary market value of the sword will then depend of the attribution. A daito in shirasaya with so-so attribution will probably fetch $2000-$2500 (in today's market), far below the cost of polishing & shirasaya & shinsa submission & agent handling fee. I wouldn't have anything polished & sent to shinsa unless my polisher (and you'd better use the best of the best) gives me the nod. Even then, it's a gamble, but one stacked in your favor. Having a good polisher who knows how to kantei swords on your side is like knowing how to count cards in a card game. No guaranty, but it sure helps.
Regards,
Hoanh