Usually when the phrase "n times less" is used, in which n is the number of times less, the intended interpretation is 1/n times as much.
Using this interpretation the calculations are as follows:
Sue: 1/4 x $100 = $25
Bob: 1/2 x $100 = $50
LaTasha: 1/1 x $100 = $100
The above interpretation does not make sense literally. How can LaTasha spend 1 time less than Tom and still spend exactly the same amount as Tom? Wouldn't $100 be zero times less than what Tom spent? But 1/0 is undefined! Note, several posters used the "1/n times" interpretation for "4 times less" and "2 times less" and used a completely different calculation for "1 time less".
A literal interpretation of "n times less" would mean the original amount minus n times the original amount. Interpreting "n times less" literally, the calculations are as follows:
Sue: $100 - 4 x $100 = - $300
Bob: $100 - 2 x $100 = - $100
LaTasha: $100 - 1 x $100 = $0
Interesting that 2 posters used the "1/n times as much" interpretation for Sue and Bob, but the literal interpretation for LaTasha.