PayPal today announced that it has agreed to purchase Paydiant, an East Coast startup that provides white-label mobile payment systems for such retailers and banks as Wal-Mart (WMT), Subway and Capital One (COF).
No financial terms were disclosed, but Fortune has learned the sale price was around $300 million ($285m of equity, and $15m in founder earnouts). This represents a nice return for the venture capital firms that pumped nearly $35 million into Paydiant over the past four years, given that the post-money valuation on its Series B and Series C rounds were $55 million and $117 million, respectively.
For PayPal, which is in the process of spinning off from eBay (EBAY), this move makes total sense. The company has struggled to create mobile payment solutions for physical retailers and banks, at the same time that later-arriving rivals like Apple (AAPL) and Google (GOOG) have gained traction. The better question, however, is why Paydiant would sell out just as its industry is beginning to garner mainstream attention.
Here is the explanation from Jim Moran, a venture capitalist whose firm, North Bridge, originally funded and incubated Paydiant:
In addition to North Bridge, Paydiant backers included General Catalyst, Stage 1 Ventures, Sands Capital Ventures and West Capital Management.
Sign up for Term Sheet, our daily newsletter on deals and deal-makers.