Fraud itself is based on the type of light provided by the laser pointer, the way power is measured, changes made to the laser pointer and sellers who are not aware and / or dishonest.
Type of light
This laser is advertised as a green laser and must provide green light and only green light. That never happened. Nearly all green power high power laser pointers supposedly on eBay emit a combination of green light with a wavelength of 532nm light and infrared light with a wavelength of 808nm and 1064nm of light.
All genuine high-power green laser pointers have filters installed which prevent them from emitting infrared light. Laser pointers on eBay are missing this filter that has been deleted or intentionally made without. Removing the infrared filter from the laser pointer increases its strength and makes it far more dangerous.
Take a 240mW laser pointer which is commonly found on eBay as an example. This laser pointer probably only has 40mW of green light with the remaining 200mW of light being infrared light. Customers pay for a laser pointer with 240nm green light and only get a laser pointer with 40mW of light. Effectively deceive them from 84% of their money.
Another problem with the infrared filter that is missing is a very dangerous laser. Infrared light spreads like a torch beam compared to a green light in a narrow beam. Visible green lights can be avoided but infrared light because they are invisible cannot be avoided. Most safety glasses that protect the green light are fully transparent to infrared light. This means someone who wears safety glasses and uses one of these lasers is less likely to avoid light and is far more likely to suffer damage to their eyes.
The power of most laser pointers will reach its peak in the first few seconds then stabilize at a much lower level than the peak. A reputable seller will give average strength as the advertised power. EBay sellers, on the other hand, use peak power as the advertised power. This is very deceptive because it misleads people into thinking the laser is far more powerful than it really is.
This laser pointer is only designed to handle power from around 5mW to 10mW. The seller modifies the laser pointer by increasing the power from the battery to the laser diode so that the diode emits a stronger laser beam. The problem with this is that diodes are not built to handle higher forces and will have a much shorter life cycle and are likely to burn. Many eBay lasers lose power or burn completely in a matter of hours or even minutes. The lens in the acrylic coating laser pointer is also not designed for increased power and tends to be damaged with reduced or completely failed performance.
These eBay sellers are not laser experts and generally have little or no understanding of the laser pointers they sell. This means they cannot provide quality advice or recommendations and the level of support and service they provide is minimal. Their general response to customers when there is a problem with the laser pointer is to send it back as a replacement. Given that laser costs are no more than shipping costs, most customers reduce their losses at that time.
Laser pointers with a power of more than 5mW are classified as dangerous items and are not allowed on eBay. If you have been tricked by one of these sellers, you can threaten to report it to eBay and maybe their account is suspended or even closed.
If you pay by PayPal, you can also open a dispute for items that are not as described. This dispute may not be decided for you, but most sellers are willing at that stage to issue you a refund. If you pay by credit card, you can restart your bill with your credit card company in the same way with a greater chance of success than PayPal.
The last choice is bluffing. Claims that you will contact eBay, police, and government departments responsible for consumer affairs in their country if they do not issue you with a refund. Considering they sell items that are prohibited by eBay and are illegal to sell (legal to own) in a number of countries, these cliffs are very effective.