Wow, that is a truly mind boggling array.
It will be interesting to watch and see what it finally goes for.
Some quick math and guesswork: The seller says he estimates he paid "over 75000 British Pounds". That is 123000 US dollars, lets round up to 125000, since he/she said it's "over" 750000 pounds. I'm sure the seller would like to make a little profit for his trouble, let's say 20% ... making the collection worth $150000.
I have no idea what the average price per piece is for Snap On stuff but let's just pick a number, say $30 (this is a critical part of the equation and is probably way off, but...), that would mean (minus the tool box) there are 3975.333 pieces. Let's say 4000 pieces.
If the buyer wanted to liquidate the collection in one year on ebay, he would have to list one lot of 11 items, every single day, for one year. And, if the seller wanted to make a 20% profit, (putting the tool box back into the equation), he would have to average a little more than $493 sale price for each lot in order to get back his $150000 and make 20%. That's with buyers paying all shipping. There are 1000 other ways to play with the numbers.
Hmmm, if someone wants to stake me, I'll quit my job, liquidate the collection and split 50/50 with you

Don't know if I could get it done in only one year though. You wouldn't want to 'flood' the market. Then again, if you type Snap On into the ebay search engine, you get 85872 listings, so, maybe the market is already flooded.
Anyway ... wow!