You can find affordable bikes at secondhand stores, online marketplaces like Craigslist or Facebook Marketplace, garage sales, or through local bike shops that offer sales or discounts.
On craigslist
Ebay, craigslist, yard sales.
Try Craigslist or yard sales.
You can find cheap pocket bikes for less than 200$ online at sites such as minipocketbikes.com and other trusted sites. You might be able to get a good cheap one craigslist or ebay.
You can find exercise bikes for cheap on eBay they are normally new or used or you can buy them new in argos or some others exercise shops. Exercise bikes are very popular so they aren't hard to find.
Chubby's Cruisers is a website that specializes in selling parts for cruiser bikes. They can be accessed at www.chubbyscruisers.com.
One can purchase cheap speedway bikes at many retail locations, both in person and online. Examples of such locations that sell speedway bikes include online bike retailers or online auction sites such as eBay.
You can find affordable bikes for heavier riders at specialty bike shops, online retailers, and secondhand stores. Look for bikes with sturdy frames and higher weight capacities to ensure durability and comfort.
Go to the nearest junk yard and find parts to bikes...or take apart old bikes you find. Make sure you use the lightest parts. (especially the frame).. Clean them up and make yourslef a bike. :)
Cheap BMX bikes can be found on eBay, Kijiji, Craigslist, Bike Warehouse, Halfords, Walmart, Bicycles Direct, Amazon, Vital BMX, BMX Shop and DK Bikes.
Depending on the brand and model of the motorcycle, would determine how cheap one could find one. One could visit the Discount New Bikes website to find motorcycles at a lower price.
Assuming that you have a motorbike, you can find relatively cheap accessories online at websites like http://www.motorcycle-superstore.com/, which has a wide variety of accessories for different types of bikes.