Why the Discontinuity in Taxes and Fees?

[WilliamK]

I've noticed that the taxes and fees have weird jumps I was pricing out possible bids to Boston Logan airport for various size cars and found weird results for two day rentals.  For example:

 

• $50/day Total: $137.8 Economy 
• $51/day Total: $165.77 Economy  A jump of $27.97!!!

 

• $48/day $125.98 Compact 
• $49/day $125.67 Compact  A lower price by $0.31???
• $50/day $128.10 Compact  Lower than Economy car by $9.70!!!
• $51/day $130.57 Compact  Lower than Economy car by $35.20!!!
• $52/day $134.98 Compact
• $53/day $171.12 Compact  A jump of $36.14

 

• $49/day $128.23 Mid-Sized
• $50/day $137.80 Mid-Sized Same price as the Economy car???
• $53/day $144.19 Mid-Sized
• $54/day $137.98 Mid-Sized A lower price by $6.21???
• $55/day $176.47 Mid-Sized A jump of $38.49!!!

 

What the heck is going on?  Is this a bug or intentional on their part to trick you into paying a lot more by giving bidding approval to ones where fees favor themselves?

 

[thereuare]

Lots of possibilities to explain the above... what dates are you searching for? (and are you searching for the same dates for each car class above?)

 

However, the more important question is if the above are cheaper than you can get thru conventional booking channels?