The iPad currently accounts for somewhere in the neighborhood of 70% of all tablets worldwide. Microsoft is desperate to claim some of this market share and push Apple and the iPad down to only 50% by mid 2013. To do this, Microsoft is planning on unleashing 32 Windows 8 based tablets before the end of the year is up.
The main part of this strategy seems to be based on the idea of flooding the market with tablets. Some of these tablets could hit the market as entry-level and come with a price tag of under $300...before tax. This would put them in the range of Amazon Kindle Fire and the rumoured Google Nexus tablet.
Apple could have some tricks remaining in order to combat these new tablets. There is that undying rumor of a smaller, cheaper iPad. Also, Apple makes quite a nice profit on the iPad. The profit is somewhere around 50%, so Apple has a large amount of leeway in the pricing of the regular iPad, if the rumor of the smaller iPad proves false.