mpbiv,
Hi and welcome to the forums!
You're doing the eBay thing correctly. Always check the shipping charges. Like you said $20 for a Bit/MicroSizers is a good price, but shipping costs bring the total up close (and sometimes more) to retail.
In most cases, I would think you're only saving a couple of dollars. AND you still have to wait for it!
The only way to really save is to buy in quantity.
Let's say that a seller is offering $20 for one Bit. Let's say shipping is $10. That's $30, same as retail.
But, if you bought 5 Bits @$20ea. and combined shipping was , let's say $20 then you'd be paying about $24 per car. But you're still forking over $120 and you still have to wait!
You'd be better off going to your local hobby shop and buying the Lancer there. You'll have it right away and you'll be supporting local businesses.
Save eBay for those hard to find items. Although, once in a great while you can find a bargain there...