WotC has to be about sales unfortunately as they are a business. However I don't think it is quite as bad as it sounds. The gametable comes 'free' with the subscription which also includes Dungeon and Dragon magazines and a rules compendium. I think other people do elements of all of those better for free. However it still seems a decent package for the cost of 2 print magazines a month so I don't feel WotC are being completely unreasonable with the pricing they are using for these products. However that may just be because I am looking on from the perspective of the UK pound which makes $15 pretty affordable
As this is only a subscription service, I don't see how this being bought by someone else as a gift, or as an impulse buy really affects this. Anyone who impulse buys a monthly subscription and is disappointed will drop it after a couple of months and go elsewhere. The other apps just need to reach these disaffected users with advertising, good word of mouth and pretty screenshots so the disaffected know what they are missing elsewhere.
As for rptools succeeding, I think they already have. There is a solid and loyal user base for what is first and foremost a hobby project. As I understand it maptool was never intended to be a business. It is a fun free app developed for fun and the love of a type of gaming. Trevor is happy to keep coding it as long as people give him fun and challenging extras to code in and (most importantly) post good feedback whenever a game goes well with it. I can't see users migrating away from maptool given we seem to have a developer who does it for love, gives it away for free, tries to incorporate specific requests into the programme on the time-scale of a month or so and is willing to talk directly with any user experiencing problems until those problems are resolved. When WotC provide that level of service for free there may be a question but I can't see that being too cost-effective!
The paying apps are a different matter as they are actually in competition with WotC.