I live in unincorporated Boulder county, so there's still an advantage to buying online, I only pay CO and RTD taxes on my Amazon purchases, no city tax. That's less than 5% instead 
of the almost 9% I pay at brick/mortar stores in either Boulder or Longmont. For large ticket items that's a hefty discount. Also, I'm not certain what happens with purchases from small ebay retailers, I do not think they are required to keep track of sales.